Multiple Chargers

I'm not going to get into a Pmatch here, but this is what I did for cruising yacht owners for years before the depression shut us down.

You will do much better to either separate the bank into sections if you can and charge each individually with small chargers or get one big charger and try to charge the assembled bank. If you buy a free standing 3+stage converter charge now, it can be temporarily connected to your house bank and properly installed later.

If you put multiple charges on any single bank, you will not get the full rate from all of them. I know, I have had to diagnose this a number of times and made some good money doing it. This advice is free and based on decades of experience and other people's money.

If the chargers you buy are any decent kind of automatic (suggested) then they will back down in their set-point order as soon as the bank voltage gets anyplace above dead. It does not matter if it is a stand-alone, MPPT solar controller or the main engine alternator, the same holds true based on my experience and the expensive instruments that I use to diagnose these kinds of issues.

Matt

If you want to PROVE whether multiple chargers do or do not contribute to the total amps going to your battery try this.

Take a good heavy jumper cable and hook it to your battery bank where you would normally connect the positive clamp from your charger. Connect the negative clamp or clamps to the batteries like you would normally. Now instead of connecting the positive clamp to the battery connect it to the other end of the jumper cable. It will now work the same as you normally connect things. What you can now do is put the amp loop of a digital multi meter around the jumper cable and SEE what is going to the batteries. Connect the second charging device the same way and so on with as many as you want. After adding a charging device recheck the amps passing through the amp loop. This simple test will show you whether it does or does not help to use multiple chargers. It is important to use a heave wire jumper cable so it doesn't induce resistance into the path. The batteries need to be at a low SOC to make this work. If they are fully charged this won't tell you anything. If you are a DIY guy like me it is a interesting project when you are bored because it is Winter and you are not our RVing (-:

Jim

One note about chargers. This is probably obvious, but worth mentioning... it doesn't hurt to get a five stage charger over a three stage. This gives you access to desulfate and equalizing charge abilities via a pendant.

Just buy one single 40 amp charger and use it. It will keep your batteries charged unless you try to run things like a water heater thru your inverter.

WIth multiple chargers if they are ALL absolutly identical in their settings, then they will all work together.

IF they are SMART chargers, odds are one of them will work, others may or may not.

IF one of them is a "DUMB" (old fashion) single stage, it will overcharge your batteries in all odds less you watch it like a hawk.

So go ahead and hook up mulitple (Best thing they both work, worst only one does. It won't hurt anything.

BFL is the multiple charger king, listen to what he says.

Find the recommended aggregate charge rate for your batteries and do not exceed it. It may be less expensive to replace the head unit in your converter and be less likely to cause battery failures. Progressive Dynamics has a replacement unit for power centers http://www.progressivedyn.com/pd4600_converter_replacement.html or buy one of their standalone units.

Like the man says "Hookem up and see!" You need to keep voltage within rational limits. My 500+ amps aggregate charger input works like a champ.

Multiple chargers works, but you have to learn how to get them all going depending on the set-up. For instance it is usually better to start the lowest voltage charger first and then start the higher voltage ones in sequence.

Sometimes you need to start the portable first, then turn on your converter even if the converter is the lower voltage charger. Solar can be going too or turned on last depending on what works at the time. You have to try out different sequences until you learn how your things like to do it.

If the higher voltage charger is already on, then the lower voltage charger might decide there is no work to do.

In the above picture, you see the 1093 which has 14.8 voltage in with some older Vectors at 14.6v. I have to start them first, then the 1093. Some chargers don't care they just get going.

You don't have to break up the battery bank and give each battery its own charger as you can see in the picture with four chargers all on the one battery bank. However you can clamp on to individual batteries if you run out of room on the posts to clamp to. That just means you might not see all the amps showing on the Trimetric if the shunt is not included for some chargers.

As the battery voltage rises, the lowest voltage charger quits first as the spread between its voltage and the battery's voltage shrinks to nothing and each charger drops out in turn until only the highest voltage charger is still adding any amps until it tapers out

If two equal voltage chargers are on they will add their amps as long as the battery will accept them. Once acceptance rate is down to the rating of one of the chargers you can yank the other. eg battery can accept 80amps at first, so two 40ampers will do 40 each for 80. later it will be say 30 and 30 for 60. Once it gets to 20 and 20 for 40, you can yank one and the other goes back to 40 and counts down from there again.

Matt is totally wrong. You can use any number of charging devices at the same time and they will ALL contribute to the charging amps.

When I am driving down the road on a hot summer day my engine alternator is charging my house batteries as well as the chassis batteries. I am running the generator to power our two rooftop AC units so that is two. I have a 800w solar system on the roof so they are also contributing to the charge. That is three. They are all contributing amps to the total charge.