What I learned about maintaining batteries while boondocking

hammick wrote:
TooTall thanks for the info. Over Thanksgiving we boondocked for four days in the shade so had to use my 2000w genset to charge batteries. I used my Schumacher manual charger on the 25a setting. Only lower setting is 2a. It got the job done but when the amps started to taper during absorption the volts went above 16a. Did you track the voltage when charging at 10a?

I used it today at 17 amps, I don't recall ever seeing that kind of voltage. Usually High 14's and then it shuts down. I've got to do some charging tomorrow, I'll see what voltage it max out at.

TooTall thanks for the info. Over Thanksgiving we boondocked for four days in the shade so had to use my 2000w genset to charge batteries. I used my Schumacher manual charger on the 25a setting. Only lower setting is 2a. It got the job done but when the amps started to taper during absorption the volts went above 16a. Did you track the voltage when charging at 10a?

TooTall2 wrote:
Here's the review on the Craftsman. I'm not pushing Craftsman although mine is spot on with my inline DC meter up to 20 amps. I haven't tested above 20 amps DC.

DC Clamp on Ammeter

Mine also reads closely with my shunted Ammeter at 40 amps, and in line with my digital multimeters reading 0.08 amps of LED. I trust it.

Just not with anything but alkaline batteries inside it. NImh AAA's had readings 20% off, and when the first pair of Alkalines got old and tired, amp and voltage readings were out of whack with reality and easy to notice.

I use my stand alone as needed, works great.

Chum lee wrote:

DanNJanice wrote:
Just curious, is anyone concerned about the high voltage output from these fast chargers? I know the smart charger that I have at home ramps up to 16V when it is charging. Is there a chance that other electronic devices could be damaged if used while charging?

In the video, if you look at the size of the battery cables and clamps coming off the portable charger, there is NO WAY they could handle 75 amps (@+-12V nominal) for more than a few seconds without overheating, hence the term "engine start or boost charge." It's designed to put substantial amps in a near dead battery short term for starting purposes, not long term bulk charging. If you have the proper power supply, you don't necessarily need excess charging voltage to quick charge a battery. Yes, excess voltage (above +-15.5V) can damage 12V electronics and resistance type electrical consumers. Typically equalization is a low amp, higher voltage process not meant to be used for bulk charging. Kudos to the 12 amp charger in the video for bulk charging @ 17 amps. My older Schumacher 10 amp charger won't. The circuit breaker trips in a few minutes at anything above 9 amps continuous but it does eventually get the job done. A smart charger would be a better solution.

Thanks for posting the video.

Chum lee

Totally agree with your cable size comment. In fact, the WFCO would do a much better job if RV makers would put something bigger than #8 gauge wire (in my case) running 10' or more. (I think the WFCO is getting a bad rap due to improper wire size.) I'm sure this is why my WFCO goes to a trickle charge way too early which is why I used the stand alone charger.

Here's the review on the Craftsman. I'm not pushing Craftsman although mine is spot on with my inline DC meter up to 20 amps. I haven't tested above 20 amps DC.

DC Clamp on Ammeter

Kudos Post Harvey51...

For accuracy in all modes my Uni T, beats the snot out of a Craftsman clamp on. When I have to refer to a 100mv Manganin shunt to resolve error that impresses me. So the Sears unit gets donated to friends in the auto repair shop. I'm going with another and possibly two more Uni T clamp on meters before I head south. That said a Craftsman is plenty accurate enough for the Handyman.

BFL13 wrote:
If 14.4 is the upper safe limit then please inform Trojan Battery (and others) that their specified charging voltage of 14.8 is unsafe.

Also note that 14.8 is at 77F. At 35F the equivalent voltage is 15.2, which is of course, over 15.

To achieve these correct voltages, you will need an adjustable voltage charger, or have temperature compensation. The standard RV converter can't do them.

Thanks for those numbers, BFL. My Black and Decker smart charger charges at 15 volts for a few minutes in its regular charging cycle. And in its desulphate treatment I think it goes a little higher. I have run desulphate on a battery in my daughter's car but I think I disconnected it from the car. Will make sure next time. The regular cycle seems to do no harm though I have never left the fridge on when using it on the RV.

To whoever is looking for a good reasonably priced DC clampmeter, I suggest this $30 UNI-T, which works very well for me. I was impressed right away when I found it's voltage range was very accurately calibrated (I checked with a voltage standard reference). Accuracy in current measurement diminishes with current and it is not very useful below a quarter amp but I expect that applies to all clampmeters. When buying a clamp meter read very carefully to make sure it can measure DC current - some say AC/DC meaning the voltage feature. Look for the term "Hall Effect", which they use to measure DC current or details of the measurement ranges as in this description.
Clampmeter on ebay

I also am a big fan of the battery monitor with Amp hour counting and continuous display of battery % of full charge. I have been happy with the 25 amp version of this cheapo monitor: Battery monitor on ebay

At these prices you can have a clampmeter AND a battery monitor.

I like to think in "Steps"

Tough to beat a 60 amp charge rate. From whatever type of charger. But when a smart charger fails to work beyond a certain battery fill level then let a manual charger take over. Full charging does not have to be done every day. But it is so very easy to twist a timer dial then between television NASCAR laps glance at an ammeter or voltmeter. The difference in amperage between say 13.6 volts and 14.8 volts is astonishing. So is the extra gasoline generator money remaining in the wallet.

I like manual voltage regulated chargers. They do the work remaining after a smart charger says "I quit!" Most good solar systems will do the same however it's role reversal time: Let the smart charger run until its tongue hangs out then let the solar do the rest. Configuring an intelligent charging regimen is highly personal. What works perfectly for one person will probably prove woefully wrong for the next person.

While just about anything will run circles around a WFCO.... There is another whole level up from just 17 amps.
Easy to get 60+ amps out of a properly wired three stage converter and make that generator earn it's keep.