battery gurus help reqd

Submitted: Friday, Jan 27, 2006 at 14:47
ThreadID: 30166 Views:2894 Replies:14 FollowUps:34
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trying to charge a 100a/h SLA battery from a 80w solar panel via 20 amp regulator. Green light on regulator is on, indicating full charge but I'm getting a reading of 12.08 and it won't budge after 3 hrs charge. I've got a couple of voltmeters, both show the same reading. I'm getting a reading of 18.93 on the solar and 14.42 on the battery leads. I had the battery given to me, so maybe it could be buggered. I can run the fluoro light off the battery, so with about 50% charge I'm gettig something out of it but I just can't top up the charge.
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Reply By: Member - Collyn R (WA) - Friday, Jan 27, 2006 at 15:39

Friday, Jan 27, 2006 at 15:39
Exactly where are you measuring the 12.08 volts? - ditto the 14.42 volts.

What is voltage across battery after an hour or two - with and withoiut light switched on.

What type of regulator?

Please state exactly how the bits are connected.
Collyn Rivers
AnswerID: 151294

Follow Up By: Steve - Friday, Jan 27, 2006 at 16:13

Friday, Jan 27, 2006 at 16:13
Hi Collyn,

12.08 is across the battery after 5 hrs, now. No change.

It reads the same with my little 12v flouro light running.

the solar connection on the regulator reads 19.30 (connected)

the battery connection on the regulator reads 14.58 (connected)

Just to clarify the 80w panel is connected to the battery via 20 amp regulator
FollowupID: 404910

Reply By: Notso - Friday, Jan 27, 2006 at 16:23

Friday, Jan 27, 2006 at 16:23
Don't forget an 80 watt panel will only put out around 6 amps if you are lucky.

It would be interesting to see how many amps the battery is accepting. Can you put an amp meter between the solar panel positive and the battery positive and see how many amps it is actually putting into the battery.

Even at 6 amps it will take something like 30 hours of charging to bring the battery up to full charge. The amount of amps the battery will accept drops off as the charge increases.

Have you got a standard 10 amp charger that you can put on for a day or so?

AnswerID: 151309

Follow Up By: Notso - Friday, Jan 27, 2006 at 16:39

Friday, Jan 27, 2006 at 16:39

Interesting info on SLAs
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Follow Up By: Steve - Friday, Jan 27, 2006 at 16:44

Friday, Jan 27, 2006 at 16:44

at the solar and battery positives I get a reading of 4.61

the battery reading isn't going up at all (over 5 hrs)

I do have a 6 amp charger but first wanted to see the solar at work

I have that site bookmarked but it doesn't address this problem as far as I can see
FollowupID: 404914

Follow Up By: Notso - Friday, Jan 27, 2006 at 17:04

Friday, Jan 27, 2006 at 17:04
Yep, it was just some info on how to look after em.

If it's only putting 4.6 amps into the battery it is going to take a while to charge your battery.

One of the things the battery makers recommend is that a charger should supply about 10 to 13% of the batteries Amp Hour Capacity, so for a 100 AH battery a minimum of 10 to 13 Amps would be recommended for Charging.

The only other thing, is there a high resistance somewhere, and it could be internal with sulphation on the plates.
FollowupID: 404915

Follow Up By: Member - Gary W (QLD) - Friday, Jan 27, 2006 at 17:28

Friday, Jan 27, 2006 at 17:28
4.6 amps is approx the rated current for 80watt panel. BP 80watt is rated at 4.76A.
If your batt is only half charged (50amp hours) it will take 50 devided by 4.6 hours of charge to bring the battery to full charge. Remember the charge is related to the suns intensity and time of day so you may not be getting the full charge all daylong. If your batt has become stratified (left at a low rate of charge for some time) it will take longer to bring the acid off the bottom. A batt charger will help to do this. You havn't mentioned what rating yor batterys capacity is stated at. For solar applications it is normally the C100 rate. Just remember you can safely charge a lead acid battery only to 10% of the C10 rating. If your 100A/H batt is has the C100 rating that will mean about 8Amps max. If you have a hydrometer check its reading - should be about 1.200-1.300 if fully charged.
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Follow Up By: Steve - Friday, Jan 27, 2006 at 19:19

Friday, Jan 27, 2006 at 19:19
11 hours????? Not that I'm in any hurry but half an hour it went from 12.08 to 12.48 so I was hoping for better, even bearing in mind the charge slows as it gets near to capacity.

It's a 100ah battery and sealed, so I can't use a hydrometer.

Might pay to invest in one of those megapulse battery restorers with 5 batteries to run.
FollowupID: 404960

Reply By: Peter 2 - Friday, Jan 27, 2006 at 16:53

Friday, Jan 27, 2006 at 16:53
Personally if using a non fixed solar panel (ie you put it out in the morning and disconnect it in the afternoon ) for camping duties you don't need a regulator or a discharge diode and removing both of these will maximise the input into the battery.
No harm will come to the battery or panel as long as you monitor the charge state with your trusty multimeter.
I've come across quite a few campers in your situation trying to charge batteries with panels and quite a few get it wrong, ie the panel capacity is usually far below what is required to keep up with consumption especially when running frig's and small panels don't usually require regulators if only connected when camped and are packed away of an evening.
AnswerID: 151311

Follow Up By: Steve - Friday, Jan 27, 2006 at 18:36

Friday, Jan 27, 2006 at 18:36
this 80w panel is certainly enough to keep my fridge running with hardly any loss, conditions permitting.
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Reply By: Member - Gary W (QLD) - Friday, Jan 27, 2006 at 17:13

Friday, Jan 27, 2006 at 17:13
Hi Steve,
You have problem with regulator or a setting on your regulator. The 18/19 volts your are reading is the "open circuit" voltage produced from the solar panel. This is a correct voltage so your panel is working correctly. The 12.08 volts across you battery suggests your battery is close to fully charged. It appears however the batt is not receiving any charge from the panels. What brand of regulator do you have? It may be the battery has been charged and regulator has gone into a float mode. If you apply a largish load across the battery - that should push the reg into charge mode and you should see an increase in voltage across the battery. Depending on your regulator settings, you may even see as much as 15volts when batt is coming up to full charge and reg is in "boost mode". I would look to see if a reg setting is not right. If reg is set correctly you should not see a diff in voltage at "solar" and "batt" - regardless of the state of charge in batt they should read the same. If you have a Plasmatronic PL20 (20amp) - check the settings that the voltage is set to 12v.

AnswerID: 151314

Follow Up By: Steve - Friday, Jan 27, 2006 at 17:51

Friday, Jan 27, 2006 at 17:51
yep. It's the bloody regulator. I'm new(ish) to this and I've had to bodge up a suitable connector from solar to battery - anyway it's galloping away now 12.22 and climbing.

I might add, in late October I played around with this and wrote on a piece of masking tape a reading of 12.35. So it's been sat in the garage since then and lost .27 down to 12.08. Anyway, I'll see how far that takes it. Probably put it on the charger o/night
FollowupID: 404928

Follow Up By: Steve - Friday, Jan 27, 2006 at 17:55

Friday, Jan 27, 2006 at 17:55
FollowupID: 404931

Follow Up By: Steve - Friday, Jan 27, 2006 at 18:32

Friday, Jan 27, 2006 at 18:32's either stopped or r-e-a-l-l-y slowed down. Still got full sun on it but the sun is fading/getting weaker.

So, assuming I get 12.49 - 12.50, which is about 90% charged, is it any use me putting it on the charger o/night bearing in mind it's only a 6 amp job and not a fancy 3-stager, or will I be better off leaving it until morning and see if the solar will get it up to 12.60........and ............ if so, do I stop at 12.60 or will it stand a bit more as long I keep my eye on the meter?
FollowupID: 404946

Follow Up By: Notso - Friday, Jan 27, 2006 at 18:43

Friday, Jan 27, 2006 at 18:43
You will need to bring it up to something like 13.8 volts, with some batteries it's even more. to get it "Fully Charged"
FollowupID: 404952

Follow Up By: Mike DiD - Wednesday, Feb 01, 2006 at 21:49

Wednesday, Feb 01, 2006 at 21:49
"So, assuming I get 12.49 - 12.50, which is about 90% charged"

- definitely not. If you are DIScharging a battery, this wmay be true but NOT when charging.

You need to have AT LEAST 13.5 volts at the battery to be at 90% charged.

FollowupID: 406075

Reply By: Steve - Saturday, Jan 28, 2006 at 09:49

Saturday, Jan 28, 2006 at 09:49
Thanks for the help so far, guys.

Last night I knocked it off with a reading of 12.50 and came down to a 12.35 reading this morning. I presume that's why they say disconnect and let it sit for six hours before taking a reading. Anyway, it's back on again (12.65 currently) and I'm going to try to get it up to the 13.8 suggested earlier. So, having done that, I will disconnect and no doubt the reading will drop again after a few hours.

Do I keep on charging it up in "sessions" until it holds 13.8? I presume when I get up to 13.8 and disconnect, it will drop again, to maybe, let's say 13.5 and then I re-charge again until it only drops to say, 13.68 or something, until the gap between what I have and 13.8 narrows to nothing.
AnswerID: 151413

Reply By: Member - Collyn R (WA) - Saturday, Jan 28, 2006 at 10:34

Saturday, Jan 28, 2006 at 10:34
I suspect your system is more or less working OK.

Note - battery is very unlikely to be badly sulphated. A sulphated battery shows a high voltage reading in such circumstances (not a low reading). This drops rapidly and sharply when the charge is disconnected.

No need to disconnect the battery at night. Just leave it alone for a day or so.

You may have theregulator wired incorrectly - this reduces charge. Many are wrongly connected - even those done professionally.

I repeat my query. how EXACTLY do you have the wiring from the solar module to the regulator and the battery? Tell me what wire you have going to where.
Collyn Rivers
AnswerID: 151423

Follow Up By: Steve - Saturday, Jan 28, 2006 at 11:43

Saturday, Jan 28, 2006 at 11:43

I have the Solar panel pos & neg cables going to the relevant points on the regulator and the battery pos & neg is linked by two cables from their relevant points on the regulator. So, solar to regulator (pos & negs) regulator to battery (pos & negs). The regulator has 4 x connection points altogether.

I have taken the regulator out of the equation since yesterday morning when I was apparently getting no charge to the battery. I have since managed to get a decent charge to the battery (still ongoing) without the regulator and am keeping an eye with frequent readings. btw, when I disconnect the solar from the battery, the reading does drop sharply. As a said earlier, last night I disconnected at 12.50 (it immediately started to drop) and woke up to a 12.35 reading. I'm now up to 12.86, which I presume will drop when I disconnect.

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Reply By: Member - Collyn R (WA) - Saturday, Jan 28, 2006 at 13:43

Saturday, Jan 28, 2006 at 13:43

As suspected your regulator is incorrectly wired.

Take the lead from solar positive DIRECTLY to the positive of the battery itself (NOT via the regulator).

Then take a second lead (it can be quite light) from that battery positive BACK to the Batt +ve terminal on the regulator.


That Batt +ve terminal is where the regulator gets its reference of battery voltage.

As you (and many others!) have it, the regulator is currently getting that voltage reference from somewhere between the 12 or so volts on the battery and the higher voltage on the solar module. The reference voltage is thus higher than the battery voltage. This causes the regulator to think the battery is far more charged than it is - so it cuts back the charge accordingly.

This is why you were getting a higher voltage reading on the regulator Batt +ve than across the battery. It also indicates that the cable from the solar to the battery is far too small (I know this because you have already indicated the voltage drop - and it's excessive).

In summary - it is essential to wire a solar regulator EXACTLY as shown by the maker. That may may not appear to make any sense (it appears to use a redundant lead) - unless you know the reason why! Many people take the short cut that you have described (ie. Solar +ve to Reg Batt + - and then to battery +ve. It works still - but not well. Sadly even a few professionals put them in like this!
Trust this works
Collyn Rivers

AnswerID: 151457

Follow Up By: Steve - Saturday, Jan 28, 2006 at 14:51

Saturday, Jan 28, 2006 at 14:51
thanks for that I said before I've been running it directly from solar to batt quite successfully all day now. I took up your suggestion and re-arranged the cabling as you instructed only to find the bloody reg has totally died on me. It's going back. It's one of those little black "Super Solar" regulators with gold lettering - I'm sure you've seen them as they seem to be popular. If you have any suggestions regarding an upgrade, I'm all ears. Then I can try the cabling arrangement you suggested. As I have about 5 batteries in use around the place would you recommend one of those Megapulse battery restorers?

I've put the solar/batt back on a direct link. btw, this is a spare batt and not connected to car or caravan.

Question #2397798: If 12.6 is regarded as fully charged what am I doing taking it well beyond that figure, up to 13.8. Is that the difference between the accepted 80% charge and 100% charge?
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Follow Up By: Mainey (WA) - Saturday, Jan 28, 2006 at 18:12

Saturday, Jan 28, 2006 at 18:12
I use an 80wt Solarex solar panel controlled by a Steca solar regulator and can get as high as 14 'plus' volts showing at the battery while the sun is shining when the Steca is in boost mode.

Have just checked the system and it's presently showing 13.2v at the battery on the Steca LCD screen, which is 'normal' when in sun and fridge not running, the panel is putting 2.4 amps back into the batteries, because the fridge is connected and has recently turned off, (cycling, temp showing 0.8 degrees) so the regulator is getting the battery system back to it's 'normal' position, when battery system is low the solar panel will put the full 4.8+ amps, to recharge the batteries.

The figure of 13.2v is the ‘regulated’ voltage being allowed into the battery by the Steca, not the true battery voltage as the Solar panel is putting out close to 20v.

(the Steca solar regulator, unlike the model Collyn refers to, has all six cables, Solar, Fridge and Battery directly connected through it)
FollowupID: 405126

Follow Up By: Steve - Saturday, Jan 28, 2006 at 21:03

Saturday, Jan 28, 2006 at 21:03
Hi Mainey, was hoping you might turn up. As I said before my regulator died on me and I've been charging directly from the panel. Before the sun started to fade I was getting well into the 14.s but I know it's not a true reading and I'm sure I'll wake up to a much reduced reading tomorrow. checked a few minutes ago (after 4 hrs rest) and it's 12.72. Next query is; how far should I take it?

Amazing how just a little shade, only about 20cms into the corner of the panel really reduces the charge. Also, after 5 pm it started going backwards - from what was a false reading - I suppose once it has stopped charging it goes back to a truer reading. This is the first hands on stuff I've done so please make allowances.

FollowupID: 405143

Follow Up By: Mainey (WA) - Sunday, Jan 29, 2006 at 12:24

Sunday, Jan 29, 2006 at 12:24
Steve, what brand of Solar panel is it ??

Kyocera have the shading problem, however their power conversion factor as a % when in full sun is superior to (possibly) all other panels? and if you want a panel that works really efficiently you may as well buy the best available performance, because if your aware that the panel won’t work in the shade you won’t put it there - will you :-)

You ask "how far can you take it" - if it was charging via the (working) solar regulator indefinitely, however in your case now if you monitor the battery often, try for at least a few days and as mentioned above it will take a while to get a true fully charged battery from a 80wt solar panel, your presently adding plenty of 'voltage' but not really deep charging the amperage into the battery, yes the amperage may be going up in number, but not as sufficiently as could be expected from a 10 amp 240v battery charger, however yes in ‘time’ it will be ok.
This would have happened because the battery has been deeply discharged to the point of being ‘flat’ and it takes time to get it back to fully charged with only a 4.8 amp solar panel from this situation. Remembering the 4.8 amp is the maximum amperage and not the realistic average amperage put out by the panel, as for many hours per day it WILL be well below this number.

Remember you are charging 17 or maybe even 20+ Volts, depending on the specifications of the solar panel, into a 12v battery, you really have to expect a problem after a while if charged continuously, maybe it will only be loss of fluid caused by overheating, but it could buckle the plates if it’s a 17 plate crank battery due to excessive heat build-up within the battery and the battery is totally stuffed then, Deep Cycle batteries have fewer but thicker plates, and will often still succumb to heat affected buckling of their plates, rendering them also to the scrap heap.

There may also be sulphation on the battery plates which will not be removed by a 80wt solar panel and that's where the Megapulse Series III, (not I or II, as ‘III’ can be used with multiple batteries, you say you have 5, at the same time) would be beneficial to your battery system, it will do the batteries no harm at all. I have a 'III' connected 24/7 to my two Deep Cycle batteries, so maybe that’s why they are approaching five years old now and still holding charge :-)

Obtain a "quality" solar regulator if you are going to be using the solar system in a camping situation often, a major benefit is a large LCD screen, so you can see when the panel is working at it’s very peak output, particularly when aiming for the optimum sun position, it saves guessing and fiddling with extra gauges and gives better performance in quicker time. I use a Steca ($225), the Plasmatronics ($310) are also very good, stay clear of the elcrapo end of the market as you have a problem now and may just repeat it.
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Follow Up By: Steve - Sunday, Jan 29, 2006 at 16:18

Sunday, Jan 29, 2006 at 16:18
Mainey, First of all, is 12.70 100% charged? This is where I get a bit lost because I thought 12.6 or more was fully charged. So, when you say "yes it in time it will be ok" (end of 2nd para) do you mean I'll get it to say, 13.8 and if so, can you explain how, if it is already "fully charged"?

The solar panel is a Photowatt PWX 80 from Solar Sales, Welshpool, W.A.
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Follow Up By: Mainey (WA) - Sunday, Jan 29, 2006 at 19:53

Sunday, Jan 29, 2006 at 19:53
Yes, technically, the open Circuit Voltage, the voltage of a battery when it is not delivering or receiving power, is 2.11 volts for each fully charged battery cell, which equates to 12.66 for a fully charged 12 volt battery, therefore ~12.7v is fully charged, when written as only one decimal point L0L, however on different testers it may read as 12.6v or 12.8v, reason being it reverts to the nearest number, eg, if the battery was actually 12.64v it would read 12.6v or if it was 12.66v it would read 12.7v.
A test meter has only to be out a few % to get an untrue number, however if you use the same meter all the time and the fully charged reading is always 12.8v then one day it goes up to and stays at 12.9v you have a difference somewhere, which does not mean it’s good or bad, however it’s a difference and maybe should be looked at.

'Fully charged' can only be tested accurately when the battery has 'rested' for some time, hence a battery showing 12.4v could actually still be fully charged -> IF it was tested shortly after powering a fridge or lights etc, and the electrochemical reactions within the battery had not settled down, if the same test was done a few hours later the ‘rested’ voltage would definitely be much higher!

"yes it in time it will be ok" (end of 2nd para) do you mean I'll get it to say, 13.8 and if so, can you explain how, if it is already "fully charged"?
Steve, what you are actually seeing when testing at the 12v battery, and assuming the 12v battery is still connected to the solar panel, the solar panel is in the sun and is actually producing power, (any power at all) is the voltage with-in the battery, and this includes the solar panel input at the time.
Tis exactly the same to use the car alternator as an analogy.
The car alternator charges the 12v battery at about 14v or 15v, if you put a multimeter on the battery when the engine is running it will read between 14v and 15v and when you turn the engine off the battery voltage will reduce to the power available only in the battery, eventually reducing to it's a fully charged state.
FollowupID: 405240

Follow Up By: Steve - Sunday, Jan 29, 2006 at 21:32

Sunday, Jan 29, 2006 at 21:32
haaa, now then, first of all apologies for the "12.7". I was being lazy. it actually read 12.70. My meter is actually a little belter - I didn't get it from Go-Lo y'know - Supercheap or nothing for me. If it ends with a "0" I leave it out. Sloppy, I know. Never mind, so, back to the "fully charged"; after it's had a nice little rest (overnight) and it reads 12.70, (that's better) I presume it's not gonna get any higher, because that is as full as it will ever get. I think I got a bit carried away (duh) when somebody mentioned getting it up to 13.80. They obviously meant whilst on charge and I was getting giddy thinking my battery was going to give me a final reading of 13.80 LOL I wish.
Anyway, 12.70 it is, which is a lot better than the 12.08 I started with and thought it was a dicky battery. Dicky regulator more like.
FollowupID: 405267

Follow Up By: Mike DiD - Wednesday, Feb 01, 2006 at 22:01

Wednesday, Feb 01, 2006 at 22:01
The voltage on a fully charged (well-rested) battery varies with a lot of factors - temperature, battery-chemistry.

My 80aHr AGM measures 13.0 volts many days after being disconnected from the charger.

Battery voltage will only ever give a rough indication of state of charge.

FollowupID: 406081

Reply By: Member - Collyn R (WA) - Saturday, Jan 28, 2006 at 21:43

Saturday, Jan 28, 2006 at 21:43
Suggest Plasmatronic PL 20 - (a) it's good, (b) there's a hell of a lot known about them.

Fully charged battery is 12.6-12.8 volts when OFF CHARGE and well rested - with no load on it.

To achieve this the on-charge voltage may go as high as 14.8-14.9 volts. If workingh correctly, the solar regulator is likely to hold it atthat for an hour or two - then reduce to about 14.2 volts for a bit - then to about 13.4-13.8 volts.

Re Megapulse. Can be very effective in restoring sulphated batteries. Did extensive tests a few years ago. - and currently doing long-term trial with a 48-voltMegapulse unit on our 48-volt property battery bank (24 by 640 amp/hour two-volts cells). Is slowly restoring the capacity.

Collyn Rivers

AnswerID: 151533

Follow Up By: Steve - Saturday, Jan 28, 2006 at 22:41

Saturday, Jan 28, 2006 at 22:41
many thanks Collyn. I'll look into that regulator. I should be Ok, with all batteries topped up and ready to go now. I'm hoping it'll hold at about 12.70, which was my last reading.

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Reply By: Steve - Sunday, Jan 29, 2006 at 09:10

Sunday, Jan 29, 2006 at 09:10
12.72 this morning;) that'll do me.

thanks for the input guys unless you've any further comment
AnswerID: 151576

Reply By: Steve - Sunday, Jan 29, 2006 at 09:17

Sunday, Jan 29, 2006 at 09:17
oh, one more thing: I checked my N70 under the bonnet = 12.42 which is 80% and normal for a cranker. My aux battery, an AGM 110 a/h reads 12.75. Is this because the Redarc allows a full charge through to it or because the AGM itself allows more charge through?
AnswerID: 151580

Reply By: Member - Collyn R (WA) - Sunday, Jan 29, 2006 at 11:09

Sunday, Jan 29, 2006 at 11:09
AGM batteries charge to a slightly higher level. Down to about 60% discharged they also operate at about 0.3-0.5 volt higher - another benefit.

Do remember that a conventional lead acid battery is not fully charged until it reaches about 14.7- 14.8 volts whilst on charge. This drops very rapidly to about 12.6-12.8 volts off load. Typically however even a very minor load will drop the voltage to about 12.5-12.55 volts.

What is happening is that a voltage measurement only shows what is happening locally around the interface between the plates and the electrolyte (the acid/water mix). It can be seen as the voltage on the surface of the plates. The charge energy however is held within that electroyte - and there is always a time lag before that is available in the form of an electric current.

The thicker and fewer the plates the longer this lag (many hours for deep cycle batteries). Thus instant voltage measurements of deep cycle batteries are all-but meaningless (except to show the meter is working!).

AGM batteries have less lag, thus a voltage measurement gives a better (but far from 100% accurate) indication of charge.

Trust this helps
Collyn Rivers

AnswerID: 151593

Follow Up By: Steve - Sunday, Jan 29, 2006 at 21:34

Sunday, Jan 29, 2006 at 21:34
Thanks Collyn. I'm getting there.

btw, I'd be interested to see how you go with the Megapulse.

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Reply By: Stuart - Sunday, Jan 29, 2006 at 18:22

Sunday, Jan 29, 2006 at 18:22
Hi guys, just my 2 bob's worth. I had one of those crap black box regulators and found that another problem is that they cut out when the panel hits about 20 volts. I have an 80watt BP Solar and it will hit 25 volts in the middle of summer. I spent endless hours watching a multimeter trying to figure out why my battery was going flat in fantastic charging weather. I eventually disconected the dam thing and then the battery really started to sizzle. Literally. I have bought a decent regulator now. I have had a Megapulse III on my sulfated main cranking battery for 6 months and have had no improvement. This is the second one as when I complained that the first one didn't work and that I thought it was just a box with some flashing lights they asked me to send it back. They sent me a new one as apparently the old one was faulty. I have used the new one on 3 different batteries and have had no improvement. This is however just my experience.

Thanks for the thead everyone it has been very enlightening. Cheers & Beers.
AnswerID: 151625

Follow Up By: Steve - Sunday, Jan 29, 2006 at 21:36

Sunday, Jan 29, 2006 at 21:36
interesting regulator experience. Think I'll get myself a good un.
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Follow Up By: Member - Collyn R (WA) - Monday, Jan 30, 2006 at 11:31

Monday, Jan 30, 2006 at 11:31
I did a series of extensive tests on the Megapulse for a CMCA technical note about three years ago.

It certainly reversed sulphation on the ten deep cycle batteries on which I tried it (proven by before and after -discharge/time testing. My 48-volt unit is also demonstrably working on my big (24 by 2-volt cells) home battery bank. The unit was less successful on deeply sulphated starter batteries. With these the deposits tend to build up on the bottom of the cells - and eventually partially short out the plates - if that happens the Megapulse is not effective.

I feel the main application is for deep-cycle batteries that are not optimally charged or used. (A correctly charged and used deep-cycle battery does not seriously sulphate - hence less need for this form of protection.

The most thorough independent testing by an authoritative German institute showed that it was successful more than 80% of the time.

Do bear in mind that pulsing is now a recognised technique that is being routinely included in many recently introduced up-market chargers.

It is not as new as many think- my TWC smart alternator regulator (designed by the Australian marine electrical engineer John Payne and marketed for a time by Hella)) used it in the 1980s. I stil have one on my OKA.
Collyn Rivers

FollowupID: 405345

Follow Up By: Flash - Tuesday, Jan 31, 2006 at 22:45

Tuesday, Jan 31, 2006 at 22:45
I've had outstanding results using a Megapulse. We have one which is moved from vehicle to vehicle to caravan etc, and while fitted it sits on charge so works 24/7.

We restored a defunct battery in my son's old Corolla. It sat on charge for three days when he bought the car and wouldn't crank the engine at all. Three or four weeks on the Megapulse, and it's been running his car for a year now, still going.
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Reply By: Member - Collyn R (WA) - Wednesday, Feb 01, 2006 at 10:04

Wednesday, Feb 01, 2006 at 10:04
The Megapulse suffers because at first sight it seems like just another of those innumerable devices that promise all (often ignoring fundamental physical laws!) yet deliver nothing. Early over-promotion possibly did not help.

In practice however it really does do virtually everything now claimed for it - with acceptance helped by the vendors' money back guarantee.
Collyn Rivers

AnswerID: 152232

Follow Up By: Steve - Wednesday, Feb 01, 2006 at 10:56

Wednesday, Feb 01, 2006 at 10:56

do you think the Basic model will do the job?

I have two cranking batteries, an AGM (aux on 4x4) a deep cycle (caravan) and an SLA that I recently acquired for zilch that I was playing with at the weekend.

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Reply By: Member - Collyn R (WA) - Wednesday, Feb 01, 2006 at 12:16

Wednesday, Feb 01, 2006 at 12:16
Basic model of what, Steve?

Re battery voltages. Dont get too hung up on exact numbers. Fully charged voltage is temperature dependent. The higher the temperature the lower the voltage at which it is fully charged. It also depends on the original specific gravity of the electroyte. Whilst ready-mixed electrolyte is typically 1.250 (when poured into an empty battery at manufacture) this can and does vary.

It is usually lower for deep-cycle batteries than starter batteries.

For clarity I need to add that when a battery gasses it is only water that is lost (not acid). This is why only distilled water is added. Never acid (unless there is an accidental spill).

Best to see a fully charged battery as being somewhere between 12.6 volts and 12.8 volts when rested and off load. AGMs tend to 0.5 volt higher.
Collyn Rivers
AnswerID: 152257

Follow Up By: Steve - Wednesday, Feb 01, 2006 at 21:25

Wednesday, Feb 01, 2006 at 21:25

I was referring to the Megapulse in the follow-up to which it was attached. I thought there were different models/levels of the megapulse battery restorer? Perhaps not. The one I've seen was about $120 from memory.

One other query. As I have a bit of an assortment of batteries, (a 100a/h SLA, a 100 a/h AGM and a 75 a/h deep cycle) would it not be advantagous/possible for me to link two of them together in series? Or due to their differences, is that not possible/advisable. My 100 a/h is my aux. under the bonnet and the deep cycle came with the caravan. I have the SLA sitting around spare. I've been swotting up in your Caravan edition today ready for my big try-out. Oh, I have one 80w solar panel.
FollowupID: 406068

Follow Up By: Steve - Wednesday, Feb 01, 2006 at 21:27

Wednesday, Feb 01, 2006 at 21:27
....I intend adding another panel at some future date when the cook isn't paying attention;>)
FollowupID: 406069

Follow Up By: Mike DiD - Wednesday, Feb 01, 2006 at 22:11

Wednesday, Feb 01, 2006 at 22:11
"would it not be advantagous/possible for me to link two of them together in series?"
- only if you want lights to be VERY bright - for a very short time - you would have 24 volts !.

To retain 12 volts you need to connect all batteries in parallel. As long as the batteries are similar chemistries they can be charged and discharged in parallel. Maintenance-free batteries are calcium-Calcium and need higher charging voltages so it would not be a good idea to connect them to conventional batteries.

FollowupID: 406085

Follow Up By: Steve - Thursday, Feb 02, 2006 at 07:06

Thursday, Feb 02, 2006 at 07:06
so, does that mean an SLA battery can be linked with an AGM?

FollowupID: 406139

Follow Up By: Mike DiD - Thursday, Feb 02, 2006 at 08:04

Thursday, Feb 02, 2006 at 08:04
In general, SLA and AGM have similar charging characteristics - checking with the manufacturer for similar Float and Cyclic voltages is always a good idea.

I assumed that you would only be slowly charging batteries that you have paralleled. If you plan to fast charge them you have to be careful - even if they are discharged while in parallel, one could hog all the charge current under some conditions.

For long battery life you should limit the initial (Stage 1) current into a battery, but keep in mind that even the most modern car Alternator does not limit battery current. Dual Battery installations using the most expensive battery isolator system do NOT sense charge current and therefore do not limit Stage 1 charge current either.

FollowupID: 406150

Follow Up By: Steve - Thursday, Feb 02, 2006 at 08:36

Thursday, Feb 02, 2006 at 08:36
we've already been thru a lot of this stuff Mike. I'm not "fast charging". I'm using an 80w solar panel with a regulator.

What I want to do is link the SLA with the AGM in series and have my 80w solar panel charging them both so that there's little (collective) discharge. Eventually I'll lash out on another panel and all my dreams will come true.
FollowupID: 406156

Follow Up By: Member - Collyn R (WA) - Thursday, Feb 02, 2006 at 16:42

Thursday, Feb 02, 2006 at 16:42

You are confusing series with parallel connections.

Two series connected 12-volt batteries (ie, positive of Bat 1 to negative of Bat 2) will result in 24-volts not twelve.

The connection you are after is parallel (positives connected together and negatives connected together).

I would personally be wary of parallel connecting batteries that have substantially different charge/discharge needs or characteristics.

I would not (for example) personally do or recommend parallel charging an AGM and a deep-cycle battery - nor any other type of battery with a calcium/calcium battery.
Collyn Rivers

FollowupID: 406275

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