Sterling battery to battery charger

[oltrunt]

I just completed the installation of a Sterling BB1230 in my little bus. I have just begun trials with it and this is what I've found to date:
1) STUDY the installation manual--lots of tricky concepts there.
2) Keep in mind Ohm's Law. Voltage equals Current times Resistance. When I first started the BB1230 it was playing to a brand new fully charged pair of Trojan deep cycle golf cart batteries. The BB was getting 14.4 volts from the alternator (12v, 110 amp) and outputting 14.6v. As a test I loaded the batteries with an inverter and all the LEDs I could turn on and allowed the batteries to draw down over night to 11.2v. I next shut off the load and fired up the bus engine. Same input voltage but the output voltage was down to 12.3v!???! After much gnashing of teeth I thought to measure the current input. I borrowed a DC clamp meter and discovered the BB was charging the battery at 26.7 amps--just shy of the 30 amp max output of the device. As a double check I disconnected the BB and switched on my house battery charger (a Progressive Dynamics 9245C converter and measured its output at nearly 45 amps--its max amps. I let the PD9245C charge the batteries up to 12v and then switched back to the BB1230 unit. All was well as the voltage output was again at 14.6 which was the charging voltage I had programmed into the unit. I like to look at it this way; if you monkey with any one aspect of Ohm's Law, the other two will change. A run down battery has less internal resistance to current (amps) than a nearly charged one. This explains the seemingly low output of the BB and its subsequent miraculous recovery on my test run.
3) Had I a larger alternator I'd have used the Sterling BB1260 (60 amp) unit to fatten up the charge rate. A 24v unit is also available in both 30 and 60 amps.
4) All the BB models are three stage and programmable to various battery types and requirements.
5) Since I use a standard 12v group 24 battery to start my genny and run the air compressor that powers the pneumatic door and the brakes on the toad, I feel comfortable with hooking it via manual switch to my start batteries/alt. The g24 likes to be drawn down quickly and recharged quickly as does the start battery.

Having had the typical experience with England's Lucas Electric (home before dark and all that) I checked out Sterling for smoke and finding none went with their product. We'll be on the road now for a week or so often dry camping and doing a good bit of driving. I'll have a better feel for the BB when we get back.
Jack

[bobofthenorth]

Don't ever run any 12v battery down below 12 volts resting.  You just took a bunch of life out of that battery by that one incident.

[buswarrior]

Thank you for proving that observing voltage alone tells a busnut NOTHING.

Why did you set the voltage at 14.6?

If you set out on a long drive with fully charged house bank...?

Thanks for sharing!

Happy coaching!
Buswarrior

[oltrunt]

Actually, Trojan recommends 14.8v for bulk/absorption rate and 14.6v is as close as the BB will come without going up to 15v.  The float rate is 13.3v for open batteries-- 1% above Trojan's recommendation.

If I start out on a long drive with fully charged batteries the BB goes to float.  Jack

[buswarrior]

Thanks!

So this new beast IS smart!

Yet another worthy variable to consider in designing a coach electrical system...

Let the pissing matches begin!!!

Happy coaching!
Buswarrior

[richard5933]

I'm glad to hear that you are having success with the BB charger. I warned you about the manual - it's not an easy read.

We just got back from a two-week trip. About half of it was dry camping and the Sterling BB charger easily handled charging the house batteries.

Now that I've used both a solenoid to charge house batteries and the Sterling, I would opt for the smart charge of the Sterling any day.

[buswarrior]

Now the other way to employ one of these relatively low powered chargers...

Put the big alternator to the house bank, with a modern regulator, and use the BB to keep the starts charged...

Oh what fun we can have?

Happy coaching!
Buswarrior

[richard5933]

Now the other way to employ one of these relatively low powered chargers...

Put the big alternator to the house bank, with a modern regulator, and use the BB to keep the starts charged...

Oh what fun we can have?

Happy coaching!
Buswarrior

Guess it all depends on the set up and the size of the battery bank. I've got about 780Ah on the house bank. Trojan recommends charging at 10% of the capacity. The 24v-ot-12v Sterling we have outputs up to 70 amps @12v, which is right in line with these recommendations.

[oltrunt]

Real good Buswarrior!  I always gauge the attractiveness of an idea by how close I get to running my home 40 gal hot water tank cold while standing, thinking, under the shower spray.  It'll probably take me a couple of baths to ponder that suggestion.  Jack

[sledhead]

I put 400 watts on the roof just to top up the house batteries when needed

dave