Charging Batteries In Parallel......

[crappie dog]

When charging batteries that are wired in parallel do you charge the one the onboard charger is connected to and after it it charged it charges the other one in parallel or do you have to charge the batteries seperately?

[HOTSPOT]

You should charge the batteries separately in order to get the best absolute charge.

No two batteries are alike, you should only use them in parallel while discharging.

Several companies make switches that will assist with making this simple.

A simple ON/OFF battery switch hooked between the positive lead of batt 1 and batt 2 will do the trick.

[Barnacle Bill]

Do like Hot Spot said unless your onboard charger has seperate leads for the batteries. Funny you should bring that up now, I believe my onboard charger is shot.

[HOTSPOT]

Bill,

I just upgraded to the Pro Mariner Pro Sport 20 (20 amps on demand, two banks).

I had the BPS XPS 5/5 made by Pro Mariner and it lasted two years. I talked with the great folks at Pro Mariner and they told me the charger I had was way under sized for my use. They gave a great promo deal on the upgrade, basically half price.

The Pro Sport 20 has a two year warranty also.

Get the biggest baddest one you can afford.

[justfish]

If you do charge with one charger, hook the postive lead of the charger to one battery and the negative lead to the other battery. Use at least ten amps. Check out this web site:http://batterytender.com/connecting.php/#9

[Barnacle Bill]

I was looking at them. I need a 3 bank but I believe they are on sale right now.

[CrappieHead]

9. Two Batteries in Parallel, One Charger


Batteries connected in series strings can also be recharged by a single charger having the same nominal charging voltage output as the nominal battery pack voltage. In Figure 8, a single 24-volt charger is connected to a 24-volt battery pack.

In Figure 9 we see a pair of 12-volt batteries connected in parallel. This 12-volt battery pack is connected to a single 12-volt charger. Note the blue wire designated W1. The purpose of this wire is to balance the voltage drop evenly across both batteries and each wire during charging. This is not critical for lower current chargers, but when you start to get into the 10 amp and above range, the voltage differential can be significant. The blue wire W1 must be connected to the opposite end of the battery pack as the black wire at the top of the battery pack.

When batteries are connected in parallel, only use one charger. Do not connect a charger to each battery, unless you break the electrical connection between the batteries. The reason is that the chargers will very likely complete one or more their charging subroutines (charge modes or stages) at different times. That means that each charger would be trying to bring the battery pack to a different voltage level. Depending on how the chargers are configured to prevent a reverse polarity connection, the charger with the lower voltage output could possibly draw current from the charger with the higher voltage output, or even from the battery pack that it is trying to charge. If the chargers' reverse polarity protection mechanism includes a solid state, unidirectional, voltage controlled, current switch (like a diode), then this is not a big problem.

[CrappieHead]

I am running two 12 volt batteries in parallel for my 12 volt trolling motor. I understand when connecting my charge I should connect it to the neg (-) ground on battery A and the pos (+) ground on battery B.

My question is should I connect my trolling motor leads the same way, or can they be connected both to one battery?

<I sent this question to [email protected] today and will post the answer I get back.>

[Barnacle Bill]

I am running two 12 volt batteries in parallel for my 12 volt trolling motor. I understand when connecting my charge I should connect it to the neg (-) ground on battery A and the pos (+) ground on battery B.

My question is should I connect my trolling motor leads the same way, or can they be connected both to one battery?

<I sent this question to [email protected] today and will post the answer I get back.>

Since they are connected together, you can connect the motor to either battery.

[BeauxBeaux]

If you do charge with one charger, hook the postive lead of the charger to one battery and the negative lead to the other battery. Use at least ten amps. Check out this web site:http://batterytender.com/connecting.php/#9

I use 2 of the big yellow batteries from Walmart to run my electronics. I charge them as stated above and have no problems but I remove the fuses to the electronics when charging. I run a big trolling motor and 2 eagle 320's. My bilge pumps and motor are hooked up to the starting battery and in 3.5 yrs I have never charged it. Ol'Ray