Limiting Current to Trailer While Driving

Try an RV supply outfit, they may have an isolator/regulator combination.

You practice of deep discharging followed by a long period without charging is not good for your batteries (even deep discharge).

To lower the charge rate below what you system can withstand is going to require longer charge times.

[quote]Try an RV supply outfit, they may have an isolator/regulator combination.[/quote]

I'm looking for a cheap alternative. It's just a 14' aluminum boat, not a $30k bass boat, LOL.

[quote]You practice of deep discharging followed by a long period without charging is not good for your batteries (even deep discharge).[/quote]

I agree, but I don't use the electric all that much anymore. Just occasionally, so it doesn't get THAT much drawdown. It just gobbles amps so quick that I can't keep a fuse in it. When I DO draw it down a bunch, I put it on a charger at home, and do the desulfate regime pretty regularly.

"Try a light bulb as a limiting resistor. Cheap and easy."

I like cheap and easy.

Hence my asking about resistors or resistor wire.

This comment only amplifies MJB's recommendation for using a light bulb in series with the charging circuit for the deeply discharged battery.

1. If you place the lamp and socket in the vehicle, where you can see it, the lamp can act as a "high-charge" indicator. I suggest using a front turn-signal lamp, at least. The headlight option is a good one, but hard to mount.

2. It is cheap. It only costs the socket.

3. The lamp should be mounted where the kids won't break it while playing in the back seat. Maybe in the trunk - up high - where you can be sure the lamp has gone out before starting your trip.

Good luck.

There are charge controllers built for just this purpose. I am sure an RV store will have what you need.

Same post as Automotive.

http://cr4.globalspec.com/thread/55333/12v-Current-Limiting-While-Charging-Trailer-etc

How good are you at making things

http://www.discovercircuits.com/C/cur-lim.htm

http://www.thecaravanshop.co.uk/charging-systems/plug-in-systems/transformer/charger-unit-18a/prod_205.html?review=write

http://www.johncooperandsons.com/12v/caravan-split-charge-relay-p-175.html

http://www.jmbadditions.com/batteriesandchargers.php

http://www.the12voltshop.co.uk/Shop/battery-to-battery-charger-24v-to-12v-25a.html

http://www.adverc.co.uk/

http://shop.ebay.co.uk/items/__battery+split+charger_W0QQ_dmdZ2?rvr_id=&crlp=982496791_228459_228460&UA=WXI7&GUID=0051b0661270a02681903cc0ffdfee6a&agid=504838351&MT_ID=10&keyword=battery+split+charger&ff4=228459_228460

Hope this lot helps

Get a decent multi-stage charger (or two?) and charge the batteries while the boat is sitting still. I use the "Battery Minder" with good results.

http://thebatteryminder.com/

Your batteries will last a lot longer. Leaving a lead acid battery sit at a low charge level is a fast way to kill it.

As already mentioned, letting your batteries go far down will shorten their working life, even if they are "Leisure" batteries....not a good move!!

To drop the charging current, I have used several high current Silicon diodes in series as each will drop around 0.6 of a volt.....I had a similarproblem when onboard a ferry and living in my caravan, that the battery got discharged and blew its fuse occasionally when the car engine was started.....

Place a switch across the diodes to switch them out once the battery is mostly charged.....

Assuming 14.4 volts for charging and say 11 volts for the battery (hopefully never less!!), then start with 4 diodes and switch them out one after the other as the charging current drops......unconventional, but will work.......heatsinking may be needed.......

55 watt 12 volt car bulbes are around 2.5 ohms or so each (if my memory serves me well!), if you decide to use that method.....use two in series....then switch one out. Always monitor the current carefully......