Now that I have 6 Concord batteries, at ~$4k a piece, to take care off I am considering getting a GPU or a battery cart to keep at my hangar. This way I can do al the at home starts on GPU and likely extend battery life to hopefully more than 5 years for the aircraft batteries.

I have been looking at options:
This battery cart https://startpac.com/products/model-3328-special/
is about $7k after shipping cost. The company assures me this is adequate for the TPE engine and will last about 3 years + with average use of 3 starts a week. Battery replacement for this unit will be about $2k.

The MU2/TPE engine needs a 28V GPU , minimum 800 amp and 1000amp continues. According to the specs this unit should be more than capable.

My question to the group is what would I gain from buying a "real" GPU at anywhere from $20-40k vs using this battery cart?

Hilgard

I can’t tell you what you would gain. I can tell you that we did all 731 starts on the 35s on a GPU. If there was going to be any substantial time in the hangar with the batteries on, a cart was plugged in. The batteries are RG380E/44. After the batteries were past 4 years old, it was a surprise if they would pass a cap check. Maybe I could get them to pass after one or two conditioning charge procedures, but more often it was just a waste of electricity and hope.

Would taking six charged up group 31 batteries and connecting to the GPU port on the plane aid in starting at home? Ie, batteries on board plus the external batteries? Parallel, not series.

No start cart at home and I don't want to take a large battery pack with me.

Not sure why one would pick that one. I bought this one:

https://startpac.com/products/model-li2700qc-26v/

Mostly for trips to very cold airports. The starts at home are usually easy as the plane hasn’t spent the night out at 0F.

Paul

The MU2 uses the RG380E/44 as well. Currently Spruce lists them at $3884 each.

Just to clarify, are you saying that inspite of using a battery minder for the aircraft batteries, and with the aid of GPU starts, you could not extend battery life beyond 4 years?

My understanding is to the contrary, nl that the Concord incrementally loses a bit of its strength after every start, never going back to the level it was before the last start. Therefore using a GPU should prolong the life. What am I missing?

Hilgard

StartPac does sell a smaller unit, approved for the MU2/TPE 331. They have a nice video of how the engine starts quicker and cooler using that.
https://startpac.com/products/model-6028qc/
https://www.youtube.com/watch?v=F6UD2Qw ... e=youtu.be


I don't have the knowledge to "roll my own" battery cart, I would be leery of such a set up.

Hilgard

Paul

The MU2 uses the RG380E/44 as well. Currently Spruce lists them at $3884 each.

Just to clarify, are you saying that inspite of using a battery minder for the aircraft batteries, and with the aid of GPU starts, you could not extend battery life beyond 4 years?

My understanding is to the contrary, nl that the Concord incrementally loses a bit of its strength after every start, never going back to the level it was before the last start. Therefore using a GPU should prolong the life. What am I missing?

Hilgard

The unit I quoted is what Startpac recommended when I spoke with them over the phone. It has a slightly higher peak rating than yours, 2800A vs 2400A peak and 84Ah vs 10Ah. I am not really interested in having a portable unit, my thinking was to use this to extend the Concord's battery life.

I have heated hangars in Alberta and at the FBO in SD, so I do not expect to start at very low temps often.

Hilgard

I have thought about this as well but decided against it for the following reasons:
1) using battery minders and pre-heat while in the heated hangar, the engines start very fast and last a lot longer than 4 years.
2) with a start pac you have to have someone outside the plane unplugging you after start. You can hold off on door seal and open the door after start to unplug, but the engine is right next to your head and loud as hell. Your passengers will think that you are undertaking a very strange and somewhat unprofessional operation.
3) the start pac is just another battery that will also degrade with each start. I don’t know how long they last. I don’t know if you can put them on a de-sulfating minder so they last longer. If they last as long as a Concorde then you might be ahead over the long run because they cost less, but I’d assume the wear on the Start Pac battery will be much greater than that on the batteries of any one plane if it is used for all of them.
4) having a large lithium ion battery in the cabin or cargo area that was just used to start a plane seems like a concerning matter as far as fires go (I know you are not looking at taking yours along but some folks do that).

My “solution” for away starts is plugging in which heats engines and batteries, engine covers , and always using the Battery Minders at home.
I have my batteries CAP checked every 100hrs and they just seem to go and go. I fly my plane about 4 legs a week.

We’ve used that unit (or a very similar one) for the TPE-331-12 on a Caravan. Works great and is convenient for ground personnel to move. Not too heavy to put in the plane with 2 guys (eg if operating away from home base for an extended period - wouldn’t do this regularly).

Haven’t had it long enough to comment on aircraft or startpac battery longevity, but starts are quick and temps nowhere near limits.

Using a battery minder wasn’t really an option, as we had over a dozen acft, they generally flew several days each week, and if they were not in the hangar for maintenance, they sat on the ramp when not flying. We would write the install date on the batteries. When a cap check was due, if the date written on the batteries was more than four years earlier, you knew that acft would need a different set of batteries if it needed to fly in less than a week. That was because batteries older than four years very rarely passed the initial cap check. Sometimes they could be saved with the conditioning charge procedure. But the conditioning charge procedure is so time consuming, if it was begun on a Monday, there was only a slight chance you could have both batteries back up for flights scheduled for the weekend. Often batteries failed the cap after the first conditioning charge, so you’d have to try again. I learned over the years that if the battery failed the initial cap at less than 40 minutes, I was probably whipping a dead horse with the conditioning charge.
I’m sure over the years we had a few batteries go longer than five years, but the percentage that went that long had to be very small.

That is sound reasoning. However it seems replacing the StartPac battery will be less expensive than a single Concord, even on the larger battery cart that I am looking into. (Replacement cost will be <$2k)

I do have someone that can do the battery starts for me, which is what lead me to this idea. I agree, I have no interest in starting the Mits with a mobile unit, either alone or with an educated passenger. In my opinion it has to be an outside person that will not be on the flight.

Hilgard

Ok thanks. I fuss around a lot having all three planes plugged in to the BM all the time while they are at home. Although I do question myself though if it makes a difference in the long run, as I have read conflicting reports. There is also the issue of keeping them on the BM all the time vs disconnecting them once fully charged, which is the newest recommendation from Batteryminder. I believe this is a CYA recommendation due to the fire hazard of keeping them on the BM all the time.

Hilgard

The unit I quoted is what Startpac recommended when I spoke with them over the phone. It has a slightly higher peak rating than yours, 2800A vs 2400A peak and 84Ah vs 10Ah. I am not really interested in having a portable unit, my thinking was to use this to extend the Concord's battery life.

I have heated hangars in Alberta and at the FBO in SD, so I do not expect to start at very low temps often.

Hilgard

Have you thought about using a wall powered GPU such as the Hobart GPU 400? It has been a few years since I have had one, however, they were going for around $7,000 in used condition.