Megapulse and dual batteries

Submitted: Monday, May 03, 2004 at 13:36
ThreadID: 12565 Views:1841 Replies:4 FollowUps:6
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Hi folks. I have just ordered a Megapulse and was wondering if anyone would like progress reports on how I go with it. I have been doing a lot of home work on batteries over the last few months and dicovered they are a science all of their own. I have 4 batteries that it will be used on in a month by month rotation. 2 are in my Cruiser, one for the camper and one in the brides car. The camper battery is in good condition and is happy to sit at 13 volts but the other 3 are showing signs of sulfation and only sit at about 12.5 to 12.6 volts. This is after charging and the surface charge is removed. I am sick of having to replace batteries every 2-3 years. After reading articles in the archive of this forum and other sources I now know where i've been going wrong. Sulfation and under charging. Regarding dual batteries my mates and I wire them up slightly differently. We run EVERYTHING off the main battery and only use the auxillary battery to start the car if needed. This eliminates a potential danger of 2 flat batteries. EG. You have been running the fridge ect off the auxillary battery for a couple of days and it's nearly flat and someone leaves the interior lights ect on all day. Result 2 flat batteries. With our variation you always have a good battery, with no parasitic load, no matter what. Both batteries are joinned (solinoid) for every day driving. If the main goes flat then once the car is started I re-isolate the batteries so the altenator charges the main battery without having to "average" the charge rate between a fully charged and a discharged battery. This system has worked very well for a long time and we have never been caught out with not being able to start the car. Both batteries are the same. Anyway that's my two bob's worth. Thanks.
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Reply By: ianmc - Monday, May 03, 2004 at 15:18

Monday, May 03, 2004 at 15:18
Hi Stuart, I have used a megapulse on a 4 yo Delkor starter battery but I cannot prove anything by this as they sometimes last more than that.
However it has been abused & almost completely flattened on occasion.

I have found that when leaving a megapulse flashing away on a battery more more than a few days without using it the battery has been discharged by the
megapulse.

Also I recently installed a 3 plug cig. lighter type socket in the tray of my ute & connected it to the scond battery. It has an led which glows constantly
and when the voltage gets down (not sure what numbers here) the led starts flashing. This happens after a few days only when not running the truck.
Yet to measure what volts the flashes start at but its a woryy until I find out as whats the point in using precious current to run a flasher which drains the battery?

Well, both answer & question in there I guess!
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Follow Up By: Member - Jeff M (WA) - Monday, May 03, 2004 at 16:31

Monday, May 03, 2004 at 16:31
A flashing L.E.D. should not flattern any car battery in a couple of days. You sure nothing else is draining it.
I too run all my gear of the aux, including the interior lights. The only things hooked up to the starter is the start motor, glow relay, headlights and ECU. The reason the headlights are on the starter battery is that the battery controller won't give the aux a full charge if it's under 11v, even if my bat is under 11v I still might need by headlights! and it beeps when there on anyway.
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Follow Up By: Stuart - Monday, May 03, 2004 at 18:47

Monday, May 03, 2004 at 18:47
Hi Ian, thanks for your reply. I have read in the litrature some where that the Megapulse is meant to be used in conjuction with a battery/trickle charger if the battery is not being charged regularly. Also if you go back through the archive on this forum (there are only 3 threads to read) you will see that there was some concern raised about damage to the battery, over the long term, by the unit being permanently connected. That's one reason I'll be rotating mine around all 4 batteries. The blurb for the Mk2 unit I ordered claims to use 4 times less current than the Mk1 but has increased pulse energy and has some more new Do-Dads that the old one didn't. Cheers.PS. the archive is worth a look.
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Follow Up By: Member - Oskar(Bris) - Tuesday, May 04, 2004 at 08:37

Tuesday, May 04, 2004 at 08:37
I asked the Megapulse agent about the fact that mine stops flashing after a couple of hours when the vehicle is stopped and he said that they are designed to work only after the battery/charging system reaches over 12.8V and thus when the float charge drops below that (when the engine is turned off), the unit automatically stops working anyway. so I doubt that the Megapulse is flattening your battery.
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Reply By: The Banjo - Monday, May 03, 2004 at 17:28

Monday, May 03, 2004 at 17:28
Indeed Stuart....it must be a science.....damned deep subject anyway....seems us mortals may never get to the bottom of successful battery ownership and use (but there is one consolation....a lot of the 'experts' know bugger-all too). Would like to manage my batteries better but my head is too full of other issues.
AnswerID: 57038

Reply By: Martyn (WA) - Monday, May 03, 2004 at 21:54

Monday, May 03, 2004 at 21:54
Stuart,
I have a dual battery set-up in my GU, I have a smart solenoid that dictates when the auxillary gets charged, under normal cirumstances, the engine starts after the solenoid sees charge for maybe a minute it then starts charging the auxillary, this way if the main battery is flat or the auxillary is flat you don't get a neat short that either battery tries to equalise with the flatter of the two batteries when the ignition key is turned to on when you first start the vehicle. I run all my accessories of my auxillary battery so the main battery only in theory sees what it was originally designed for, this also gives the auxillary battery work to do which I have been led to believe is good for it. So far I've had this set up or four fourbies and it's worked so far. I've tried the hersy switch approach it all became to hard especially with things like "where to go next" and "Have I got enough fuel" questions are buzzing around. I'm into the automatic approach and the KISS principle. Hope some of this may help.
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AnswerID: 57096

Follow Up By: Stuart - Monday, May 03, 2004 at 22:38

Monday, May 03, 2004 at 22:38
Hi Martyn, thanks for your reply as well. Your set up is the way most people do it, but the point I was making is that the way we set up the system it's nearly imposible to end up with 2 flat batteries. Also the solinoid kicks in as soon as the key is turned which results in both batteries cranking and running the engine and there by making sure the auxilary battery is used. This puts all the cranking current though the solinoid but I have been using the same Ingrams solinoid in this way for 9 years with no trouble. As for the flat battery trying to equalise with the charged battery, I did mention how this problem was over come. Also the equalisation is not a fast reaction. It takes a while, much longer than the time it takes to hit the key and start the car. Thanks for your input though. Cheers.
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Follow Up By: Martyn (WA) - Tuesday, May 04, 2004 at 20:57

Tuesday, May 04, 2004 at 20:57
Stuart,
I don't common up the two batteries and I don't personally think it's a good idea. I've connected a small mechanical electric clock to the auxillary battery via the cigarette connection in the back, this keeps a constant very small load on the battery to keep it active. I was under the impression that the equalisation process is dictated by the charge of the flatter of the two batteries so if there is a small delta you won't see much transfer taking place, on the other hand if there is a large delta the time it takes for the glow plug light to go out on a diesel is enough to make a significant change, especially seeing the load taken by the glow plugs, I've seen this happen with my LED battery indicator. This is of course my opinions, this works for me and it's what I've been told. Hope some this helps.
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Follow Up By: Stuart - Tuesday, May 04, 2004 at 21:34

Tuesday, May 04, 2004 at 21:34
Thanks Martyn, like I said it's a science. Thanks for your input, it's nice to learn something new. Cheers.
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Reply By: Flash - Friday, May 07, 2004 at 19:08

Friday, May 07, 2004 at 19:08
Megapulse units have been available with different activation voltages.
Some will flatten a battery if left long enough with no charger.
If it activates at 12.8 volts or so it will NOT flatten the battery
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