Battery charger help needed

Submitted: Monday, Jun 06, 2005 at 19:37
ThreadID: 23646 Views:3974 Replies:2 FollowUps:4
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During cloudy conditions, when the solar panel is ineffective, I use a Yamaha 1Kva generator to charge the caravan battery. In order to run the generator for the least amount of time possible, I wish to purchase a 20 amp battery charger. I intend running it through a Plasmatronics PL20 regulator, which will result in the charger working like an expensive "smart" charger.
Can anyone recommend a 20 amp charger for me to buy please? Also, I understand that chargers rated at 20 amps might not supply a continuous 20 amp charge. Is this correct please?
Thanks everyone,
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Reply By: Grungle - Monday, Jun 06, 2005 at 21:27

Monday, Jun 06, 2005 at 21:27
Hi Dave,

Running a battery charger, your alternator or power supply through a 3 stage solar regulator will not allow the regultor to operate according to its programmed charge profile for optimum charging (it will work though to a certain degree but will never get off the 'bulk" stage). The reasons for this is that all the above only pump out around 13.5-14 volts (alternator will be higher but as its voltage increases it current decreases so will not be of any help) and a smart charger usually operates at around 14.2-14.5 volts during its bulk and absorbtion stages. The exception is if you found a power supply that supplies a higher voltage (idealy 17-22 volts) with maximum current supply at above 15 volts (if you do not use the equalise function of the regulator). This would enable the solar regulator to perform as it was designed. The problem with this though is having some sort of current limiting in either the power supply or regulator (such as the PL20 which you can program max current setting) as a solar regultor during its bulk stage operates as constant current so will suck as much as it can from the source. No protection means blowing fuses or worse, equipment.

I have gone through all the above, even built a power supply but my regulator (which is 20A) cannot be programmed for current limiting so I kept blowing fuses on the power supply as it tried to suck up to its max rating of 25A (this is why you never have solar panels that can supply more current than the regulator can handle unless you can limit the current in some way). A realy good site is this siteas it describes how to go about exactly what you want to do.

I ended up buying a 30A 3 stage charger from ebay for $370. It does everything I want but without the cost of similar items (Xantrex for example). It is identical to the Durst type and works extremely well.


AnswerID: 114673

Follow Up By: Dave - Tuesday, Jun 07, 2005 at 13:11

Tuesday, Jun 07, 2005 at 13:11
Thanks David,

Presently I use a 6 amp (4 amp continuous) charger through the PL20. The PL20 goes through its' normal boost, absorbtion and then float stages exactly as it does when I connect the solar panel through it. It does this despite the Arlec only providing 12.9 volts.
The reason I run the charger through the PL20 is because it results in the cheap Arlec working as a three stage 'smart' charger. Once the PL20 goes into the float stage the battery is holding 13.8 volts. I have been doing this for 5 years on the same battery without problem. I have the PL20 protected with fuses and have never blown one.

The Arlec is a slow way of charging the battery and I figure that a 20 amp charger will mean that the generator running time will be minimised. Similarly, I feel that a cheap 20 amp charger will be turned into a 3 stage charger by the PL20, just like the Arlec one is.

I would be very interested if you have any further thoughts on this.

FollowupID: 370566

Follow Up By: Grungle - Tuesday, Jun 07, 2005 at 16:17

Tuesday, Jun 07, 2005 at 16:17
Hi Dave,

I don't know how it could do this as a regulator cannot put 14.5 volts into a battery when the supply source is only 12.9 volts however if it works for you then I believe you have answered your own question and sould get the 20 amp battery charger.

One thing to check though is the profile settings on the PL20 to make sure that the voltage settings are right for the battery you use.

Mine which is used on AGM batteries is set to 14.2 volts for bulk and absorbtion and 13.5 volts float. This is what is recomended for my battery type by the manufacturer.

FollowupID: 370591

Reply By: Mainey (WA) - Monday, Jun 06, 2005 at 22:01

Monday, Jun 06, 2005 at 22:01
what power output do you get with cloudy conditions ??
What loss of power do you suffer in cloudy conditions ??

Why won't you run the 20 amp charger direct from the genni to the caravan battery ??
As you say 20 amp charger will not deliver the full current at all times, why not get an automatic charger that will deliver 'bulk' and then 'float' charge as required by the battery, will be faster and no problems of overcharge or even undercharge for the battery system!!
AnswerID: 114679

Follow Up By: Dave - Tuesday, Jun 07, 2005 at 13:18

Tuesday, Jun 07, 2005 at 13:18
I use a 70 watt solar panel. My daily use is 15 amps and this solar panel gives me 3.7 amps per hour in sunny conditions.
Under cloud, the power produced ranges up to about 0.7 amps.

The reason I run the charger through the PL20, is because the PL20 converts the cheap charger into a 3 stage one and subsequently fully charges the battery.

FollowupID: 370568

Follow Up By: Mainey (WA) - Tuesday, Jun 07, 2005 at 18:44

Tuesday, Jun 07, 2005 at 18:44
You state you presently receive 3.7 a/h in sunny conditions, which equates to requiring only 4 hours of sunshine daily = 14.8 amps, where you are taking out of the battery only 15 amps daily.

Basically the numbers are close enough to even with only 4 hours of sunshine daily.

You probably have a battery containing 80 to 115 amp/hours, and using 15 amps daily, you have a realistic reserve of three or four days without any significant requirement to replace the power used to run the fridge etc.

To buy and haul around a genni just to get extra o.2 amps daily, when the sun does shine is your own judgment; you could also consider starting the vehicle or going for a drive every 3 or 4 days, however on a more practical note I would check your panel performance as the o.7 amps produced under cloud does appear a low figure.
FollowupID: 370620

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