13' Scamp battery / inverter questions - bit of a newbie

[TopoFusionScott]

Hi guys, first post, really excited to find an active forum for fiberglass trailers.

I have a 2007 Scamp 13' that is new-to-us. I'm trying to figure out the electrical and battery situation and could use some help.

We put a new group 31 battery on the tongue, hoping for a little more capacity for dry camping. I have a couple questions about charging:

1) We have the 'American' converter. Am I correct that we should not leave this plugged in and charging the battery if we are not draining it daily? It will overcharge the battery, correct?

2) When plugged in using the 7 prong adapter with the TV's alternator running, I understand the battery will charge at something like 10 amps. I assume this also is not a 'smart' charger, and will overcharge the battery as well (less of a concern given that driving distances aren't usually long, and we'd usually start with a less-than-full battery).

3) Given both of these, can I prevent the converter from charging the battery simply by pulling the #1 12V fuse (labeled for the converter itself) in the box? Or will that kill the 12V system entirely when on shore power? Might there be any other way to prevent charging of the battery when it's full, short of physically disconnecting it?

Regardless, it sounds like I should plan on the American unit smoking and replacing with the Progressive Dynamics one, down the road.

Thanks for any help!

[David B.]

Welcome Scott to the FGRV forum family. If you keep an eye on the electrolyte level, and keep it topped off, you shouldn't have to worry about the charger ruining your battery. I would check it every month if left plugged in all the time. I would encourage you to attend the Quartzsite gathering in February if you get a chance. Last year there were over one hundred fiberglass eggs in attendance, and all willing to share knowledge and experiences, wine, campfire, and song. Hope to meet you there. We will be in the Lil Snoozy.
Dave & Paula

[TopoFusionScott]

Originally Posted by David B.

Welcome Scott to the FGRV forum family. If you keep an eye on the electrolyte level, and keep it topped off, you shouldn't have to worry about the charger ruining your battery. I would check it every month if left plugged in all the time. I would encourage you to attend the Quartzsite gathering in February if you get a chance. Last year there were over one hundred fiberglass eggs in attendance, and all willing to share knowledge and experiences, wine, campfire, and song. Hope to meet you there. We will be in the Lil Snoozy.
Dave & Paula

Thanks! So the American unit's charging must not be all that quick, such that it doesn't kill batteries quickly. The thing is just to not leave it plugged in, unused, for long periods of time?

I saw the Quartzsite gathering and would love to attend. We'll be at the 24 hours of Old Pueblo bike race that weekend unfortunately, but I am hoping we can get to Quartzsite for the pre-gathering to meet some folks and talk eggie campers!

[Steve L.]

• Long term life of the battery seems to be a function of the “float” voltage. The consensus gold standard Progressive Dynamics has a float voltage of 13.6 VDC. The Parallax converter common in Casitas is 14.1 VDC which is high enough to boil the fluids in the battery over time. I couldn’t find any specifications on your converter on their website so don’t know how it would compare.

• I have had a string of new Ford tow vehicles and never have had the battery recharged by the tow vehicle’s alternator. Modifications could be made to improve that and some people report GM trucks have features to allow this but I’ve never witnessed it. Many people make claims but I’m doubtful. I believe the alternator puts a “surface” charge on the trailer battery which, after the battery rests for a couple hours without a drain or charge applied, I expect the voltage returns to its partially discharged state.

In any event, the alternator charges the battery to a voltage and again, it depends on what the float voltage is.

• I don’t know. The battery goes through the converter and on to the devices. My converter (Parallax) doesn’t have a 12V fuse. Well it has a couple fuses protecting against reverse hook up. My converter does have a 120VAC breaker that can be flipped to stop the converter from converting but the 12v appliances still work. So I can (and often do during the winter) isolate the converter from the 120 VAC but I can’t isolate the trailer from the tow vehicle. I suppose one could find the wire back from the 7 pin and put a toggle in it.

[David B.]

Scott, just keep the electrolyte level topped off, because if it boils off to expose the plates to air, it will ruin the battery.

[RogerDat]

Most tow vehicle charging involves the trailer batter being on the alternator in the same circuit along with all the other auto accessories. Alternator will output power in an attempt to maintain a voltage equal to fully charged battery. Won't overcharge but may not charge all that fast either. Line voltage has to be over battery voltage to "flow" into battery, greater that difference the faster the battery charges. Analogy is filling a tire from an air tank, as long as the tank has higher pressure than tire then tire is filling up. If air tank has higher pressure tire fills faster. Eventually air tank and tire have the same pressure. This is up to the point the vehicle alternator can't keep up, then you don't have enough power to flow into the battery.


Not unheard of for "typical" alternator to be able to charge RV battery but not able to keep up with RV fridge running on 12 volt going down the road. Sucks the power from the line faster than alternator can supply so battery discharges rather than charging.


Some vehicles (GM, Ford, Dodge etc.) with a tow package will already have a circuit for alternator line to trailer hitch along with trailer brake lines. Otherwise it means pulling a wire. Some debate about how heavy a wire is required (thinner wire loses more voltage) But no one suggests anything under 10 gauge as far as I know. With many advocating for really heavy wire to like #6 or #8 to deliver as much current as possible to the battery.


Don't have your battery sitting around partly discharged. You mentioned leaving on a trip with it not fully charged. Batteries not happy to be cooked, drawn below 50% charge, or stored in a discharged condition. Battery loses some percentage of charge every day from just sitting.

[TopoFusionScott]

Roger,

Many thanks for the reply. Makes sense -- so I will not worry about overcharging while towing. Sounds like not getting much of a charge is more the issue!

We're planning to 'full time' out of the little Scamp, so we'll often be leaving a dry camp with a semi-discharged battery. Good reminder on the 50% as the ideal depth of discharge for battery life. We're going to try to stick with that, with maybe occasional dips down to no more than 20% if we need to. The trailer itself won't pull much (LED lights only + fantastic fan + furnace fan), but we both work remotely, so keeping our phones and laptops charged is going to be the challenge. I have some wiring questions I'll make a new thread for regarding that (inverters and USB ports).

Last question on battery charging: Does anyone know if the standard American Converter has any kind of voltage regulation built in, or does it just always apply a high voltage to get it to charge? People seem to say these converters are 'bad' and should not be left in for days at a time, but they can't be so bad or they would have been frying batteries left and right? I understand they aren't going to have a 4-stage algorithm and a monthly equalization cycle, but surely they don't just dumbly apply a high voltage, do they? Seems like not, based on what others have said here.

Thanks for all the replies!

[Joe Romas]

Scott.
The Parallax 6325 converter in our 1999 17' Casita has an adjustable float charge.

As far as charging phones go just install some 12v cigarette lighter out lets and use car chargers.

Joe

[TopoFusionScott]

Originally Posted by Joe Romas

Scott.
The Parallax 6325 converter in our 1999 17' Casita has an adjustable float charge.

As far as charging phones go just install some 12v cigarette lighter out lets and use car chargers.

I haven't seen any way to configure the American converter, yet.

I was originally thinking of running a small inverter out of a 12v outlet, but buying a laptop 12v charger is going to be a lot more efficient and also more simple.

So I just need to figure out a good place to permanently mount a couple of 12v sockets, and wiring them should be pretty simple.