New trailer - understand battery system

[backcountry birds]

If anyone can offer some help it would be greatly appreciated as I am new to electrical stuff.

I bought a trailer and it has two deep cycle 6V golf cart batteries. The voltage reads above 12 so that leaves me to believe they are wired in series. It has no invertor but does have a shore power plug.

1. Can anyone confirm these batteries are in series and not parallel?
2. What's the best way to charge and maintain the batteries between trips?
3. Could I use a 12 V charger to charge the two 6V and if so would I attach it to the same battery or one terminal from each or does it even matter?
4. It appears to be charging from my vehicle when towing, will it also charge if plugged into shore power or do I need a battery charger?
5. What voltage reading can I safely take the power down to without damaging the batteries and what voltage should it read when full?

 

[krick3tt]

Determine the connection by visual exam, are they N to N and P to P (parallel) or they N to P (series) then to the trailer output?

My experience with military vehicle batteries (two in series to achieve 24 volts) is to charge them separately as opposed to charging them in series. The stronger of the two will charge first if charged while in series and the weaker of the two will continue to get less charge and continue to get weaker over time. Have had several ex-military vehicles over a 20 year period.
I would think that two 6V batteries in series would respond the same way.

I have a motorcycle battery charger that charges 6v batteries and is not very expensive. I would think that disconnecting yours and charging separately would be best for their long term life. I am talking about not using them for periods of time in your trailer.

Apparently the trailer is set up to charge them together while driving your vehicle but an alternator may act somewhat differently than house current.

I am sure that there will be other that have different experience than I and may give you additional pointers and advice.

 

[Joe917]

Treat 2-6 volt GC batteries a one 12V battery. Charge them and discharge together ( do the same for 2-12V in a 24V bank).
Batteries in series should be the same size and age, assume yours are.
Use a 12V charger connected to the two terminals with cables leaving the batteries, not the short cable connecting the two.
Charging batteries in series individually is a great way to shorten their lives.
Krick3tt's battery problems are not from charging in series but from a battery imbalance during discharge.

 

[Chuck1]

1, The batteries are in series
2, depends on systems and how long you store the RV
3, 12 V charger to charge
4, maybe, time to study your system
5, stay above 50%, depends on battery type

 

[backcountry birds]

Thanks y'all! I tried to post a photo but it's saying it's too large.

My voltage seems to get up around 12.5 after driving so I guess based on the chart above I should top them off with a charger to 12.64 and not go below 12V? The previous owner told me not to go below 10.6V. These are lead deep cycle batteries. GC2-ECL-UTL
www.interstatebatteries.com/products/gc2-ecl-utl

This setup powers a Snomaster LP66 fridge, a water pump for quick showers at night, Ignition of propex heater, Amazin fan and a few trailer lights.

My truck has dual alternators. Is there anything worthwhile I could do with that to improve charging or just take what I get from the 7 pin connector?

 

[Buddha.]

A battery monitor like the victron 712 would get you a lot better idea of your battery fullness than voltage alone.

You could run heavy charging leads back to the trailer. It would have to be at least 2awg, properly fused, and isolated from your truck batteries when your truck is not running.

 

[DiploStrat]

At the risk of blowing my own horn, you REALLY need to read these three articles, otherwise you may not be able to sort out the advice you are getting.

-- Watts Up! Plan Electrical System (wordpress.com)
-- Charging Up! Battery Charge Slides (wordpress.com)
-- Doubling Up! Dual Battery Slides 2016 (wordpress.com)

They take you through the process, step by step.

Hope you find them useful.

EDITED to fix a ghastly typo!

 

[backcountry birds]

Thanks. Will do!

 

[burleyman]

It appears your batteries have removable caps for inspection. Specific gravity testers have been used for many years to determine state of charge.

 

[OllieChristopher]

At the risk of blowing my own horn, you REALLY need to read these three articles, otherwise you may not be able to sort out the advise you are getting.

-- Watts Up! Plan Electrical System (wordpress.com)
-- Charging Up! Battery Charge Slides (wordpress.com)
-- Doubling Up! Dual Battery Slides 2016 (wordpress.com)

They take you through the process, step by step.

Hope you find them useful.

This is my first post. I'm in the process of a dual battery install. Thank you Fredrick for the good info on 12V DC electrical systems. I think anyone will learn something from your blogs. Very good information and detail. I appreciate your effort and wish you and all the members here a Merry Christmas.

Chris

 

[jays0n]

Charging from the 7-pin connector is not really efficient enough to bother, if you really want to charge the trailer's batteries from the tow vehicle you need to run large gauge wiring back to it on a separate connector dedicated to charging, you can find lots of info about this on the internet and likely the links provided above. We have a solar powered house that uses large lead acid 6 volt batteries in series and it's extremely important to keep them watered. If you pull a cap and see exposed lead the batteries are not long for this world. Keep a gallon of distilled water on hand to keep them topped up, they'll last a lot longer if you do.