Question on camper converter/charger for the gurus

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Question on camper converter/charger for the gurus

Postby Camp4Life » Tue Aug 01, 2017 9:26 am

I'm concerned with my charger because it's old (1998 model). The brand is B-W and it's model 3243. This is a built-in converter/charger in the trailer and would be difficult to swap out.

I know with newer chargers, they use microprocessors and whatnot to ensure the batteries get what they need, and usually switch between 1 of 3 different charge settings. I'm good with modern electronics and use MC's in projects, but I'm not sure how something from 1988 would handle charging a battery.

When I plug in my trailer, the voltage to the battery slowly raises over a matter of hours. After 5-6 hours it's up to 13.4 volts. After ~8 hours it's at 13.8 volts. That's usually when I unplug it before going to bed because I don't really trust leaving it plugged in overnight. I'm afraid of how high the voltage might get, and I'm not sure if the voltage will step back down to a trickle charge once the battery is full. I don't want to overcharge and wreck the battery.

I'm not sure my multimeter could handle being hooked up in series for extended periods of time to monitor the amps. It's a max of 10A for a maximum amount of time (I think it says 5 minutes). I know there's some moderate amps running to the battery because the charging wire going to the battery is warm. Not hot, but it is definitely warm, though barely noticeable.

So anyone with some experience out there know about these old chargers? Do they sense the battery charge and adjust accordingly? Are they pretty reliable? Do they have built-in failsafe circuits in case of malfunction? Am I being overly paranoid?

Any info would be awesome!

Thanks :beer:
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Re: Question on camper converter/charger for the gurus

Postby John61CT » Tue Aug 01, 2017 12:59 pm

Cannot answer about that charger, but there is old stuff still working fine, sometimes the new "intelligent" bells and whistles actually get in the way.

To start, you need the mfg specs for the target battery.

The voltages you mention are low for many modern lines, but maybe would get high enough if you let it.

You really should have a way to measure actual charging volts and amps completely independently of the charger.

A battery monitor like Victron BMV-702 will do that and a lot more to ensure longevity out of whatever bank you buy in the future.

If the bank is FLA then a cheap hydrometer will tell you a lot.
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Re: Question on camper converter/charger for the gurus

Postby woodywrkng » Tue Aug 01, 2017 1:13 pm

While I don't know anything about your specific charger, or battery, I would assume the current from a proper charger will decrease to a negligible amount when you're seeing the 13.8 volts at the battery. You could check the current draw with your ammeter to verify. This is just Ohms law. With a very low difference in voltage between the charger and battery, the current will be low. Disconnect the charger from the battery and measure what the charger reads. If it's much above 14.4 volts as I recall, I would maybe think twice about leaving it hooked up to the battery long term. If the charger voltage is your observed 13.8 volts without the battery, you're perfectly safe leaving everything turned on.

Chances are your charger doesn't have anything too fancy inside btw. I think the intelligent chargers are much newer than yours. When does this wire feel warm? When charging a discharged battery, or after it's reading 13.8 volts?
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Re: Question on camper converter/charger for the gurus

Postby Camp4Life » Tue Aug 01, 2017 2:26 pm

John61CT wrote:Cannot answer about that charger, but there is old stuff still working fine, sometimes the new "intelligent" bells and whistles actually get in the way.

To start, you need the mfg specs for the target battery.

The voltages you mention are low for many modern lines, but maybe would get high enough if you let it.

You really should have a way to measure actual charging volts and amps completely independently of the charger.

A battery monitor like Victron BMV-702 will do that and a lot more to ensure longevity out of whatever bank you buy in the future.

If the bank is FLA then a cheap hydrometer will tell you a lot.


Yikes that Victron is expensive. I found a few available in Canada that have good reviews and are cheaper.

This one seems ok but doesn't show charging rates : https://www.amazon.ca/Digital-Multimeter-6-5-100V-Voltmeter-Amperage/dp/B01EUISFFE/ref=cm_cr_arp_d_product_top?ie=UTF8

This one seems a little better and shows more information including charging rates : https://www.amazon.ca/DROK-Multimeter-Charge-Discharge-Electricity-Overvoltage/dp/B01M5CWR2P/ref=sr_1_42?rps=1&ie=UTF8&qid=1501615036&sr=8-42&keywords=battery+monitor

They both use the shunt systems for proper metering. I'll just have to house the shunts on the hitch a-frame protected from the weather and run wiring inside for the displays.

woodywrkng wrote:While I don't know anything about your specific charger, or battery, I would assume the current from a proper charger will decrease to a negligible amount when you're seeing the 13.8 volts at the battery. You could check the current draw with your ammeter to verify. This is just Ohms law. With a very low difference in voltage between the charger and battery, the current will be low. Disconnect the charger from the battery and measure what the charger reads. If it's much above 14.4 volts as I recall, I would maybe think twice about leaving it hooked up to the battery long term. If the charger voltage is your observed 13.8 volts without the battery, you're perfectly safe leaving everything turned on.

Chances are your charger doesn't have anything too fancy inside btw. I think the intelligent chargers are much newer than yours. When does this wire feel warm? When charging a discharged battery, or after it's reading 13.8 volts?


I've never been able to find anything good on those chargers either because they were discontinued long ago. The battery is a flooded-cell NAPA 24RVS "deep cycle" with 85AH. I never saw over 13.8 volts, but I've never left it plugged in for longer than about 8 hours so I'm not sure if it would continue to climb. I could disconnect the charge wire from the battery once it's at 13.8 and hook it up to my ammeter, but if it's pushing 10+ amps, that current could cause quite the sparking...

The wire feels warm when it's reading 13.8 volts, after several hours of being plugged in. My battery was at 12.15 volts before I plugged it in and we had just come back from a camping trip.

If this continues to make me feel uneasy, I might have to consider figuring out how to replace the converter/charger for a new system. But I think I'll install a monitoring system before then just to get a better idea of what's going on.
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Re: Question on camper converter/charger for the gurus

Postby woodywrkng » Wed Aug 02, 2017 7:00 am

You have a pretty large battery, amp-hour wise, so you should be able to leave it attached to the charger indefinitely if the current draw sits at 850 ma (.85 amps) 0r less when fully charged. What I was suggesting is that you measure the voltage of the charger when disconnected from the battery. I'm assuming the charger is a simpler type that just applies a set voltage to the battery, at perhaps a defined current limit. If the voltage of the charger alone, no battery attached, is around 14.4 volts, no worries. If the current draw with the battery attached and charged is no more than .85 amps (1/100th the capacity of your battery), no worries.

You mentioned . . .
"I could disconnect the charge wire from the battery once it's at 13.8 and hook it up to my ammeter, but if it's pushing 10+ amps, that current could cause quite the sparking... "

When you disconnect your battery, there is no current flow, thus, no sparking, as long as you don't lay the charge wire on a ground :). Measure the volts of the charger with the battery disconnected, and the amps with it connected and at the 13.8 volts you mentioned.
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Re: Question on camper converter/charger for the gurus

Postby Camp4Life » Wed Aug 02, 2017 9:17 am

woodywrkng wrote:You have a pretty large battery, amp-hour wise, so you should be able to leave it attached to the charger indefinitely if the current draw sits at 850 ma (.85 amps) 0r less when fully charged. What I was suggesting is that you measure the voltage of the charger when disconnected from the battery. I'm assuming the charger is a simpler type that just applies a set voltage to the battery, at perhaps a defined current limit. If the voltage of the charger alone, no battery attached, is around 14.4 volts, no worries. If the current draw with the battery attached and charged is no more than .85 amps (1/100th the capacity of your battery), no worries.

You mentioned . . .
"I could disconnect the charge wire from the battery once it's at 13.8 and hook it up to my ammeter, but if it's pushing 10+ amps, that current could cause quite the sparking... "

When you disconnect your battery, there is no current flow, thus, no sparking, as long as you don't lay the charge wire on a ground :). Measure the volts of the charger with the battery disconnected, and the amps with it connected and at the 13.8 volts you mentioned.


Thanks for the info! The current draw should be next to nothing. The only thing that always draws power is the carbon monoxide detector, and I imagine it's less than half an amp. I test it though. I'll try measuring the charge voltage sans battery after work and report back. As for the sparking, I just meant while connecting/disconnecting the leads. I have to plug the trailer in while it's connected to the battery or it won't send power to the charge wire. I tried that before, and I assume it checks for a battery before attempting to charge.

Once I get this sorted, I can finally move on to adding solar :twisted:
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Re: Question on camper converter/charger for the gurus

Postby woodywrkng » Wed Aug 02, 2017 10:49 am

When I mention checking the current draw, I'm meaning the current being drawn through the charge wire to the battery being charged. While the battery is being charged, and it's fully charged at 13.8 volts. I was assuming you have an ammeter, which you would put in series with the charger to battery.

When you mentioned . . . .

"I tried that before, and I assume it checks for a battery before attempting to charge."

Perhaps your charger has some decent intelligence. In that case, all you're concerned about is the current being drawn by the battery, from the charger, when the battery reads full (13.8v). Less than an amp of current drawn at this time (the .85 amps I stated earlier) should be perfectly safe for your big battery.
Last edited by woodywrkng on Wed Aug 02, 2017 8:53 pm, edited 1 time in total.
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Re: Question on camper converter/charger for the gurus

Postby Camp4Life » Wed Aug 02, 2017 1:15 pm

woodywrkng wrote:When I mention checking the current draw, I'm meaning the current being drawn through the charge wire to the battery being charged. While the battery is being charged, and it's fully charged at 13.8 volts. I was assuming you have an ammeter, which you would put in series with the charger to battery.

When you mentioned . . . .

"I tried that before, and I assume it checks for a battery before attempting to charge."

Perhaps your charger has some decent intelligence. In that case, all you're concerned about it the current being drawn by the battery, from the charger, when the battery reads full (13.8v). Less than an amp of current drawn at this time (the .85 amps I stated earlier) should be perfectly safe for your big battery.


Yes I mean it wasn't sending any current (amps) to the battery charge wire when I plugged it in with the battery disconnected. I had the wire disconnected and used my multimeter in series to the battery. It might have a bit of a brain I guess. I'll try hooking it up in series BEFORE I plug it into shore power and see what happens then. Still also contemplating getting a 2nd battery to double my AH. Or drop the $400 for 2 new 6V 230AH batteries. 460 AH might even give me enough power for the whole summer lol We rarely use lights and only use the water pump sparingly.
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Re: Question on camper converter/charger for the gurus

Postby John61CT » Wed Aug 02, 2017 5:15 pm

Again, test the charger on a well-depleted (50% SoC) but healthy battery, log the volts and amps using known accurate test gear.

Stop when amps falls to 1% of the 20-hour AH capacity (2A for a 200AH bank).

Report the the results back here before trashing the charger.

If the above seems difficult or difficult for you, consider it an investment in your learning curve, will stand you in good stead caring for your House electrics forever.

Besides that Victron, Bogart's Trimetric and Midnight's Whizbang Jr are good Battery Monitors, both will integrate well in future with solar controllers.

Quality gear does cost money, but keep in mind banks are consumables, most permanent infrastructure will last decades.
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Re: Question on camper converter/charger for the gurus

Postby Shadow Catcher » Wed Aug 02, 2017 7:09 pm

My feeling is you are in need of a modern converter or your battery will not reach 100% SOC. Progressive Dynamics makes a replacement head unit which might fit.
http://www.progressivedyn.com/pd4600_converter_replacement.html
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Re: Question on camper converter/charger for the gurus

Postby Camp4Life » Thu Aug 03, 2017 11:29 am

Ended up working late and got my order of LED bulbs for all the lights so I swapped those and did a bit more work on the roof which is a priority. It's not leaking, but I want to make sure it won't this winter. Lots of scraping old stuff off, scrubbing, taping and sealing going on...

I tried hooking up my multimeter in series and got nothing from the charge wire. Tried putting it in series to the negative battery post and turned on some lights, got nothing, and no lights came on. I think I popped the ammeter fuse in my meter somehow and I didn't have time to run out to get a replacement. It's good for 10A so I'm not sure what happened.

For now though, it seems ok. My trailer was plugged in Monday and unplugged before bed, and my battery is still showing 12.73 volts, so at least it's charging :thumbsup:

I'll have to pick up a new fuse and try again.

I also got this:

Image

So I can have USB ports and a proper voltmeter. Tested against my multimeter and it's accurate.

I've also ordered this:

Image

Which will show all the info I need for charging and discharging. Now I just need to find good places to install these things...
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Re: Question on camper converter/charger for the gurus

Postby woodywrkng » Thu Aug 03, 2017 12:04 pm

Those gizmos look interesting. They have more features than my homemade control panel . . . .


99555
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