Adding extra batteries

[oyly]

I've started looking into adding two extra batteries to my Winnebago Via 25P. This is to give myself enough battery power to make the furnace heater fan last through a night

My main concern with this is whether or not the power converter will cope with the extra capacity. Doubling the battery capacity should double the required charging current. The Winnebago web page says the converter is only 45 amps, which makes me worry it will not be sufficient to charge 4 group 24 batteries.

Doing some math with numbers from the power converter manual: In boost mode (14,4V), a 125Ah battery was returned to 90 percent charge from 0 percent in 8 hours. I currently have two batteries with unknown Ah rating, but reserve capacity of 140, so total Ah for both batteries should be around 140Ah. Assuming these will be returned to charge at the same rate as the 125 Ah battery, the charging current should be: 140*0,9/8 = 15,75 A.

Double that capacity, and I would need 31,5 A charging current, which leaves me with 45 - 31,5 = 13,5 A free to use during boost mode charging. This seems to me like I would normally be fine, and occasionally overload the converter, which should the shut down due to either the short circuit protection or the thermal protection.

[pianotuna]

Hi,

I gave up one storage compartment to add additional capacity. I've since moved to surplus acid AGM jars. I did have a brace welded on to support the extra weight.

If I did not camp in the cold, I'd have considered using LI battery chemistry.

[oyly]

hpdrver wrote:
Where are adding the extra batteries in the 25P.

Not sure where I will add them. I see there's space underneath the car towards the rear, but that would make them quite inaccessible. I'm open to suggestions. Anybody on the forum added batteries to their RV? Where did you put them?

[oyly]

Gjac wrote:

oyly wrote:

Gjac wrote:
I would create two separate battery banks especially if you are worried about running a furnace all night while dry camping. Charge each separately with your 45 amp converter. This way you can add batteries with more amp hrs and not worry about balancing the batteries. I don't know about prices in Japan but I have not been able to find true deep cycle 12v batteries for the price of two 6 v GC batteries with equivalent amp hrs.

How would I get through the night with the furnace on if I do this? Seems I would have to get up after 4 hours to switch to the other battery bank!? 😞

I have been trying to respond to your post for the last 2 days but have been unsuccessful. My two batteries 230 ah GC type easily last through a cold night. In the summer they last 7 days and are at 50 percent SOC. What temps are you camping in? What are your other amp draws? Another option is a portable propane heater with no DC power reqs.

It was cold, just around freezing, so the batteries must have been low on capacity.

[hpdrver]

Where are adding the extra batteries in the 25P.

[Gjac]

oyly wrote:

Gjac wrote:
I would create two separate battery banks especially if you are worried about running a furnace all night while dry camping. Charge each separately with your 45 amp converter. This way you can add batteries with more amp hrs and not worry about balancing the batteries. I don't know about prices in Japan but I have not been able to find true deep cycle 12v batteries for the price of two 6 v GC batteries with equivalent amp hrs.

How would I get through the night with the furnace on if I do this? Seems I would have to get up after 4 hours to switch to the other battery bank!? 😞

I have been trying to respond to your post for the last 2 days but have been unsuccessful. My two batteries 230 ah GC type easily last through a cold night. In the summer they last 7 days and are at 50 percent SOC. What temps are you camping in? What are your other amp draws? Another option is a portable propane heater with no DC power reqs.

[Ductape]

We have a 1 or 2 or both battery switch on our banks. And two batteries will run a furnace all night.

[Gjac]

oyly wrote:

Gjac wrote:
I would create two separate battery banks especially if you are worried about running a furnace all night while dry camping. Charge each separately with your 45 amp converter. This way you can add batteries with more amp hrs and not worry about balancing the batteries. I don't know about prices in Japan but I have not been able to find true deep cycle 12v batteries for the price of two 6 v GC batteries with equivalent amp hrs.

How would I get through the night with the furnace on if I do this? Seems I would have to get up after 4 hours to switch to the other battery bank!? 😞

[Gjac]

oyly wrote:

Gjac wrote:
I would create two separate battery banks especially if you are worried about running a furnace all night while dry camping. Charge each separately with your 45 amp converter. This way you can add batteries with more amp hrs and not worry about balancing the batteries. I don't know about prices in Japan but I have not been able to find true deep cycle 12v batteries for the price of two 6 v GC batteries with equivalent amp hrs.

How would I get through the night with the furnace on if I do this? Seems I would have to get up after 4 hours to switch to the other battery bank!? 😞

[oyly]

Gjac wrote:
I would create two separate battery banks especially if you are worried about running a furnace all night while dry camping. Charge each separately with your 45 amp converter. This way you can add batteries with more amp hrs and not worry about balancing the batteries. I don't know about prices in Japan but I have not been able to find true deep cycle 12v batteries for the price of two 6 v GC batteries with equivalent amp hrs.

How would I get through the night with the furnace on if I do this? Seems I would have to get up after 4 hours to switch to the other battery bank!? 😞

[Gjac]

I would create two separate battery banks especially if you are worried about running a furnace all night while dry camping. Charge each separately with your 45 amp converter. This way you can add batteries with more amp hrs and not worry about balancing the batteries. I don't know about prices in Japan but I have not been able to find true deep cycle 12v batteries for the price of two 6 v GC batteries with equivalent amp hrs.

[pianotuna]

Buying a converter with greater capacity is not going to make much difference, because above 85% state of charge, the acceptance rate is about 12.5 amps. As the bank gets closer to 100% that rate drops. It may take four times longer to get from 85% to 100% than it does to get from 50% to 85%.

[DrewE]

The PD 92-series converters all have the charge wizard built in, which is how they differ from the 91-series converters. It may or may not have the external remote box with the blinky light and the mode change button; if there isn't one attached, it can be bought and plugged in. But even without the remote, the charge wizard circuitry is included and active.

This converter should be adequate for any battery bank you could reasonably fit in. Naturally, the larger the battery bank, the longer it takes to charge (at least after a point), and in that case a higher power converter would charge the larger bank more quickly (assuming it's set to output the same voltages). For a single battery or a small bank, the limiting factor may well be the impedance of the battery limiting the charge current, not the power output capability of the converter.

The PD converters are among the best regarded ones available, by the way.

[dougrainer]

The AMP RATING of a Converter just states how MUCH amp draw it can sustain, NOT installed to provide higher charge rates. For instance, a small 24 foot trailer will usually have a 30 amp converter as the total 12 volt amp draw with everything ON will not be over 30 amps. Larger RV's that have a lot more DC appliances and 12 volt lights will have higher AMP converters. The "charge" by a converter is a extra plus, but the OEM's do not take that into account when spec'ing out an RV. Doug

[pianotuna]

Does the existing PD converter have the wizard feature? If not I'd certainly upgrade it by adding one.